X0303 4 2008-12-03 0 0001172139 BILL BARRETT CORP BBG 0000929408 WARBURG PINCUS & CO C/O WARBURG PINCUS LLC 466 LEXINGTON AVENUE, 10TH FLOOR NEW YORK NY 10017 0 0 1 0 0001414565 Warburg Pincus Private Equity X, L.P. C/O WARBURG PINCUS LLC 466 LEXINGTON AVENUE, 10TH FLOOR NEW YORK NY 10017 0 0 1 0 0001414561 Warburg Pincus X, L.P. C/O WARBURG PINCUS LLC 466 LEXINGTON AVENUE, 10TH FLOOR NEW YORK NY 10017 0 0 1 0 0001414564 Warburg Pincus X LLC C/O WARBURG PINCUS LLC 466 LEXINGTON AVENUE, 10TH FLOOR NEW YORK NY 10017 0 0 1 0 0001157334 WARBURG PINCUS PRIVATE EQUITY VIII L P C/O WARBURG PINCUS LLC 466 LEXINGTON AVENUE, 10TH FLOOR NEW YORK NY 10017 0 0 1 0 0001322709 Warburg Pincus Partners LLC C/O WARBURG PINCUS LLC 466 LEXINGTON AVENUE, 10TH FLOOR NEW YORK NY 10017 0 0 1 0 0001162870 WARBURG PINCUS LLC C/O WARBURG PINCUS LLC 466 LEXINGTON AVENUE, 10TH FLOOR NEW YORK NY 10017 0 0 1 0 Common Stock, par value $0.001 per share ("Common Stock") 2008-12-03 4 P 0 100 18.78 A 5075188 I I Common Stock 2008-12-03 4 P 0 400 18.79 A 5075588 I I Common Stock 2008-12-03 4 P 0 200 18.84 A 5075788 I I Common Stock 2008-12-03 4 P 0 400 18.87 A 5076188 I I Common Stock 2008-12-03 4 P 0 200 18.89 A 5076388 I I Common Stock 2008-12-03 4 P 0 1900 18.90 A 5078288 I I Common Stock 2008-12-03 4 P 0 4900 18.91 A 5083188 I I Common Stock 2008-12-03 4 P 0 300 18.92 A 5083488 I I Common Stock 2008-12-03 4 P 0 800 18.93 A 5084288 I I Common Stock 2008-12-03 4 P 0 700 18.94 A 5084988 I I Common Stock 2008-12-03 4 P 0 200 18.95 A 5085188 I I Common Stock 2008-12-03 4 P 0 400 18.96 A 5085588 I I Common Stock 2008-12-03 4 P 0 100 18.97 A 5085688 I I Common Stock 2008-12-03 4 P 0 600 18.98 A 5086288 I I Common Stock 2008-12-03 4 P 0 1000 18.99 A 5087288 I I Common Stock 2008-12-03 4 P 0 1500 19.00 A 5088788 I I Common Stock 2008-12-03 4 P 0 4700 19.01 A 5093488 I I Common Stock 2008-12-03 4 P 0 2000 19.02 A 5095488 I I Common Stock 2008-12-03 4 P 0 3400 19.03 A 5098888 I I Common Stock 2008-12-03 4 P 0 2400 19.04 A 5101288 I I Common Stock 2008-12-03 4 P 0 2300 19.05 A 5103588 I I Common Stock 2008-12-03 4 P 0 2600 19.06 A 5106188 I I Common Stock 2008-12-03 4 P 0 800 19.07 A 5106988 I I Common Stock 2008-12-03 4 P 0 1798 19.08 A 5108786 I I Common Stock 2008-12-03 4 P 0 400 19.09 A 5109186 I I Common Stock 2008-12-03 4 P 0 3600 19.10 A 5112786 I I Common Stock 2008-12-03 4 P 0 2700 19.11 A 5115486 I I Common Stock 2008-12-03 4 P 0 1900 19.12 A 5117386 I I Common Stock 2008-12-03 4 P 0 5000 19.13 A 5122386 I I Common Stock 2008-12-03 4 P 0 3200 19.14 A 5125586 I I See Exhibit 99.1 See Exhibit 99.1 Exhibit List: Exhibit 99.1 - Explanation of Responses Exhibit 99.2 - Joint Filers' Names and Addresses Exhibit 99.3 - Joint Filers' Signatures WARBURG PINCUS & CO. By: /s/ Name: Scott A. Arenare, Title: Partner 2008-12-05