SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                            -----------------------

                                  SCHEDULE 13G
                                 (Rule 13d-102)

             INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT
           TO RULES 13d-1(b),(c) AND (d) AND AMENDMENTS THERETO FILED
                            PURSUANT TO RULE 13d-2(b)
                               (Amendment No. 6)*


                              UnitedGlobalCom, Inc.
                              ---------------------
                   (f/k/a United International Holdings, Inc.)
                                (Name of Issuer)



                 Class A Common Stock, par value $0.01 per share
                 -----------------------------------------------
                         (Title of Class of Securities)



                                   913247 50 8
                                   -----------
                                 (CUSIP Number)



                         Filed pursuant to Rule 13d-2(b)
                         -------------------------------
             (Date of Event Which Requires Filing of this Statement)


         Check the  appropriate box to designate the rule pursuant to which this
Schedule is filed:

         [ ]      Rule 13d-1(b)
         [ ]      Rule 13d-1(c)
         [X]      Rule 13d-1(d)


*The  remainder of this cover page shall be filled out for a reporting  person's
initial filing on this form with respect to the subject class of securities, and
for any  subsequent  amendment  containing  information  which  would  alter the
disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the  Securities  Exchange  Act of
1934 ("Act") or otherwise  subject to the liabilities of that Section of the Act
but  shall be  subject  to all other  provisions  of the Act  (however,  see the
Notes).





CUSIP NO.:  913247 50 8              13G                       Page 2 of 7 Pages

1.  NAME OF REPORTING PERSON
    I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY)

    Mark L. Schneider
- --------------------------------------------------------------------------------

2.  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                    (a) [ ]
                                                                         (b) [X]
- --------------------------------------------------------------------------------

3.  SEC USE ONLY
- --------------------------------------------------------------------------------

4.  CITIZENSHIP OR PLACE OF ORGANIZATION

    USA
- --------------------------------------------------------------------------------
               5.  SOLE VOTING POWER:

               -----------------------------------------------------------------
   NUMBER OF
    SHARES     6.  SHARED VOTING POWER:
 BENEFICIALLY      998,154 (1)
   OWNED BY    -----------------------------------------------------------------
     EACH
   REPORTING   7.  SOLE DISPOSITIVE POWER:
    PERSON
     WITH     -----------------------------------------------------------------

               8.  SHARED DISPOSITIVE POWER:
                   998,154 (1)
- --------------------------------------------------------------------------------

9.   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     998,154 (1)
- --------------------------------------------------------------------------------

10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES
    CERTAIN SHARES*                                                          [X]
- --------------------------------------------------------------------------------

11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

    1.21% (2)
- --------------------------------------------------------------------------------

12. TYPE OF REPORTING PERSON

    IN
- --------------------------------------------------------------------------------
                      *SEE INSTRUCTIONS BEFORE FILLING OUT.

(1)  Reflects the 2-for-1 stock split in November 1999.  Also,  includes 275,418
     shares of Class A Common Stock Mr. Schneider would acquire upon exercise of
     presently exercisable stock options, and includes 580,736 shares of Class A
     Common Stock  issuable upon  conversion  of 580,736  shares of the Issuer's
     Class B Common Stock, par value $0.01 per share ("Class B Common Stock").
(2)  Adjusted  for the  exercise  of options  and  conversion  of Class B Common
     Stock. Each share of Class A Common Stock is entitled to one vote per share
     and each share of Class B Common  Stock is entitled to ten votes per share.
     Holders of Class A Common  Stock and Class B Common  Stock vote as a single
     class on the election of directors.  See Item 8 concerning  the election of
     directors.




CUSIP NO.:  913247 50 8              13G                       Page 3 of 7 Pages


ITEM 1.

     (a)  Name of Issuer:

          UnitedGlobalCom,  Inc. (f\k\aUnited  International Holdings,  Inc.), a
          Delaware corporation

     (b)  Address of Issuer's Principal Executive Offices:

          4643 S. Ulster Street
          Suite 1300
          Denver, Colorado  80237

ITEM 2.

     (a)  Name of Person(s) Filing:

          Mark L. Schneider

     (b)  Address of Principal Business Office or, if None, Residence:

     The address for the Reporting Person is:
          c/o UnitedGlobalCom, Inc.
          4643 S. Ulster Street
          Suite 1300
          Denver, Colorado  80237

     (c)  Citizenship:

          Mark L. Schneider is a citizen of the USA.

     (d)  Title of Class of Securities:

          Class A Common Stock, par value $0.01 per share

(e)  CUSIP Number:

          913247 50 8

ITEM  3. IF THIS STATEMENT IS FILED PURSUANT TO SECTIONS 13d-1(b) OR 13d-2(b)
         OR (c), CHECK WHETHER THE PERSON FILING IS A:

(a) [ ] Broker or Dealer registered under Section 15 of the Exchange Act.

(b) [ ] Bank as defined in Section 3(a)(6) of the Exchange Act.

(c) [ ] Insurance company as defined in Section 3(a)(19) of the Exchange Act.

(d) [ ] Investment company registered  under Section 8 of the Investment Company
        Act of 1940.

(e) [ ] An investment adviser in accordance with Rule 13d-1(b)(1)(ii)(E).

(f) [ ] An  employee  benefit  plan or endowment  fund in  accordance  with Rule
        13d-1(b)(1)(ii)(F).




CUSIP NO.:  913247 50 8              13G                       Page 4 of 7 Pages


(g) [ ] A  parent  holding  company or control  person  in accordance  with Rule
        13d-1(b)(1)(ii)(G).

(h) [ ] A  savings  association  as  defined  in  Section  3(b) of  the  Federal
        Deposit Insurance Act.

(i) [ ] A  church  plan  that is  excluded from  the definition of an investment
        investment company  under Section 3(c)(14) of the Investment Company Act
        Act of 1940.

(j) [ ] Group, in accordance with Rule 13d-1(b)(1)(ii)(J).

If this statement is filed pursuant to Rule 13d-1(c) check this box. [ ]

ITEM 4.  OWNERSHIP

Provide the following  information regarding the aggregate number and percentage
of the class of securities of the Issuer  identified in Item 1. The  information
provided in this Item 4 assumes the conversion of Class B Common Stock for Class
A Common Stock and reflects the 2-for-1 stock split of the Issuer's common stock
on November 30, 1999.

     (a)  Amount beneficially owned:

          Mark L. Schneider  beneficially  owns 998,154 shares of Class A Common
               Stock, which includes presently  exercisable  options for 275,418
               shares of Class A Common Stock.

     (b)  Percent of class:

     The following  percentage interests are based on 81,578,682 shares of Class
     A Common Stock  outstanding  as of December  31,  1999,  as provided by the
     Issuer.

          Mark L.  Schneider:  1.21% (adjusted for presently  exercisable  stock
               options)

     Each share of Class A Common  Stock is  entitled  to one vote per share and
     each  share of Class B Common  Stock is  entitled  to ten votes per  share.
     Holders of Class A Common  Stock and Class B Common  Stock vote as a single
     class on the election of directors.  When all classes of stock beneficially
     owned by the Reporting  Person are aggregated,  the Reporting Person may be
     deemed to beneficially own voting equity securities  representing  2.26% of
     the voting power with respect to a general election of directors  (adjusted
     for presently  exercisable stock options).  See Item 8 below for additional
     information concerning the election of directors.

     (c)  Number of shares as to which such person has:

          (i)   Sole power to vote or to direct the vote: not applicable

          (ii)  Shared  power to vote or to  direct  the vote (see Item 8 below,
     which is incorporated in this Item 4(c) by this reference):

          Mark L. Schneider:  998,154 shares, includes 275,418 shares subject to
               presently exercisable options

          (iii) Sole power  to  dispose  or to direct  the  disposition  of: not
     applicable

          (iv) Shared power to dispose or to direct the disposition of (see Item
     8 below, which is incorporated in this Item 4(c) by this reference):

          Mark L. Schneider:  998,154 shares, includes 275,418 shares subject to
               presently exercisable options



CUSIP NO.:  913247 50 8              13G                       Page 5 of 7 Pages

ITEM 5.  OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS.

If this  statement  is being filed to report the fact that as of the date hereof
the reporting  person has ceased to be the  beneficial  owner of more than 5% of
the class of securities, check the following [ ].

ITEM 6.  OWNERSHIP OF MORE THAN FIVE PERCENT ON BEHALF OF ANOTHER PERSON.

         Not applicable.

ITEM 7.  IDENTIFICATION AND CLASSIFICATION OF THE SUBSIDIARY WHICH  ACQUIRED THE
         SECURITY BEING REPORTED ON BY THE PARENT HOLDING COMPANY.

         Not applicable.

ITEM 8.  IDENTIFICATION AND CLASSIFICATION OF MEMBERS OF THE GROUP.

Mark L.  Schneider is the  beneficial  owner of 417,418 shares of Class A Common
Stock (includes  275,418 shares that would be acquired upon exercise of options)
and 580,736 shares of Class B Common Stock.

Pursuant to the terms of that certain Stockholders'  Agreement,  dated April 13,
1993  (the  "Stockholders'  Agreement"),  by and among  the  Founders  and their
Permitted  Transferees,  Apollo Cable Partners,  L.P. ("Apollo") and the Issuer,
Apollo and the Founders agreed to vote in favor of three persons nominated to be
directors by Apollo and nine  persons  nominated to be directors by the Founders
in the  elections of directors of the Issuer.  The number of persons  Apollo and
the  Founders  are  entitled to nominate for election as directors is subject to
reduction  for each group if the  percentage of the Issuer's  voting  securities
beneficially  owned  by  it  is  reduced  below  certain  levels.  The  director
nomination rights expire on April 12, 2003, unless earlier terminated. A copy of
the  Stockholders'  Agreement  can be found  at  Exhibit  10.16 to the  Issuer's
Registration Statement on Form S-1 (File No. 33-61376) filed with Securities and
Exchange Commission on April 21, 1993.

The Reporting  Persons have been advised that Lawrence F. DeGeorge,  Lawrence J.
DeGeorge  and  Apollo  sold all their  Class B Common  Stock,  an  aggregate  of
9,859,336 shares,  to Liberty Media  Corporation  ("LMC") in 1999 and that, as a
consequence of such sale, those persons are no longer bound by the Stockholders'
Agreement.  Pursuant to the terms of the Stockholders'  Agreement, LMC succeeded
to certain rights and  obligations of Apollo under the  Stockholders'  Agreement
upon the closing of such transaction.  In connection with such transaction,  LMC
entered into a Term Sheet (the "Term Sheet") with the Issuer and its  subsidiary
United Pan-Europe Communications NV ("UPC"),  concerning the Issuer's securities
and other  matters and LMC  announced it had agreed to assign 50% of such shares
to Microsoft Corporation. The Stockholders' Agreement is to be replaced by a new
agreement when the provisions of the Term Sheet are fully  implemented.  Each of
the Reporting  Persons disclaims  beneficial  ownership of the shares of Class B
Common Stock held by LMC.

Some Founders have transferred at various times all or a portion of their shares
of the  Issuer to the  following  persons:  Albert & Carolyn  Company,  James R.
Carollo Living Trust,  John B. Carollo Living Trust,  Curtis Rochelle Trust, Jim
Rochelle,  the Marian H. Rochelle  Revocable Trust,  Kathleen Jaure, The Gene W.
Schneider  Family Trust,  the  Revocable  Trust of Janet  Schneider,  Richard H.
Schneider,  Robert A.  Schneider,  Susan G. Schneider and the Revocable Trust of
Henry H.  Cate,  Jr.  As a result of these  transfers,  the  transferees  became
subject to the Stockholders' Agreement. Also, in January/February 1999, Susan G.
Schneider  sold all her  shares  of Common  Stock and is no longer  bound by the
Stockholders'  Agreement. As a result of the foregoing  transactions,  1,630,720
shares of Class A Common Stock (includes  1,083,838  shares subject to presently
exercisable  options) and  9,014,588  shares of Class B Common Stock are held by
the following current parties to the Stockholders' Agreement: Albert M. Carollo,
Carollo Company,  Albert & Carolyn Company,  James R. Carollo Living Trust, John
B. Carollo Living Trust,  Kathleen  Jaure,  The Gene W. Schneider  Family Trust,
Curtis  Rochelle,  Curtis Rochelle Trust,  Jim Rochelle,  Marian  Rochelle,  the
Marian H. Rochelle  Revocable Trust, Gene W. Schneider,  G. Schneider  Holdings,



CUSIP NO.:  913247 50 8              13G                       Page 6 of 7 Pages

Mark Schneider, Janet Schneider, the Revocable Trust of Janet Schneider, Richard
H. Schneider,  Robert A. Schneider,  Henry H. Cate, Jr., and the Revocable Trust
of Henry H. Cate, Jr.

The Issuer's Board of Directors  currently  consists of eleven members,  nine of
whom may be deemed to have been  nominated  by the Founders and two of whom have
been elected at the request of LMC and Microsoft.  Upon full  implementation  of
the Term Sheet, it is anticipated  that the Founders will nominate eight members
and UPC, LMC and Microsoft will each nominate one member of the Board.

Pursuant  to  Rule  13d-4,  each  of  the  Reporting  Persons  hereby  disclaims
beneficial  ownership for purposes of Section  13(d) or 13(g) of the  Securities
Exchange  Act of 1934,  as  amended,  of the shares of Class A Common  Stock and
Class  B  Common  Stock  held by LMC,  any  other  Founder  or  their  Permitted
Transferees.

ITEM 9.  NOTICE OF DISSOLUTION OF GROUP.

         Not applicable.

ITEM 10. CERTIFICATIONS.

         Not applicable.




CUSIP NO.:  913247 50 8              13G                       Page 7 of 7 Pages


                                    SIGNATURE

After  reasonable  inquiry and to the best of the  undersigned's  knowledge  and
belief,  the  undersigned  certifies  that  the  information  set  forth in this
statement is true, complete and correct.


Dated:  February 7, 2000                      /s/ Mark L. Schneider
                                              ----------------------------------
                                              Mark L. Schneider