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 2008-12-04 4 P 0 200 17.03 A 5293689 I I Common Stock 2008-12-04 4 P 0 200 17.04 A 5293889 I I Common Stock 2008-12-04 4 P 0 1000 17.05 A 5294889 I I Common Stock 2008-12-04 4 P 0 200 17.06 A 5295089 I I Common Stock 2008-12-04 4 P 0 600 17.08 A 5295689 I I Common Stock 2008-12-04 4 P 0 200 17.09 A 5295889 I I Common Stock 2008-12-04 4 P 0 300 17.11 A 5296189 I I Common Stock 2008-12-04 4 P 0 200 17.14 A 5296389 I I Common Stock 2008-12-04 4 P 0 200 17.15 A 5296589 I I Common Stock 2008-12-04 4 P 0 400 17.16 A 5296989 I I Common Stock 2008-12-04 4 P 0 400 17.17 A 5297389 I I Common Stock 2008-12-04 4 P 0 200 17.18 A 5297589 I I Common Stock 2008-12-04 4 P 0 200 17.20 A 5297789 I I Common Stock 2008-12-04 4 P 0 200 17.25 A 5297989 I I Common Stock 2008-12-04 4 P 0 200 17.26 A 5298189 I I Common Stock 2008-12-04 4 P 0 200 17.27 A 5298389 I I Common Stock 2008-12-04 4 P 0 400 17.30 A 5298789 I I Common Stock 2008-12-04 4 P 0 200 17.31 A 5298989 I I Common Stock 2008-12-04 4 P 0 200 17.32 A 5299189 I I Common Stock 2008-12-04 4 P 0 200 17.36 A 5299389 I I Common Stock 2008-12-04 4 P 0 400 17.54 A 5299789 I I Common Stock 2008-12-04 4 P 0 600 17.59 A 5300389 I I Common Stock 2008-12-04 4 P 0 400 17.60 A 5300789 I I Common Stock 2008-12-04 4 P 0 700 17.61 A 5301489 I I Common Stock 2008-12-04 4 P 0 800 17.62 A 5302289 I I Common Stock 2008-12-04 4 P 0 800 17.63 A 5303089 I I Common Stock 2008-12-04 4 P 0 400 17.66 A 5303489 I I Common Stock 2008-12-04 4 P 0 200 17.67 A 5303689 I I Common Stock 2008-12-04 4 P 0 200 17.68 A 5303889 I I Common Stock 2008-12-04 4 P 0 200 17.72 A 5304089 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