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 17.57 A 5444211 I I Common Stock 2008-12-04 4 P 0 200 17.58 A 5444411 I I Common Stock 2008-12-04 4 P 0 400 17.59 A 5444811 I I Common Stock 2008-12-04 4 P 0 200 17.60 A 5445011 I I Common Stock 2008-12-04 4 P 0 400 17.61 A 5445411 I I Common Stock 2008-12-04 4 P 0 200 17.63 A 5445611 I I Common Stock 2008-12-04 4 P 0 400 17.64 A 5446011 I I Common Stock 2008-12-04 4 P 0 200 17.66 A 5446211 I I Common Stock 2008-12-04 4 P 0 100 17.67 A 5446311 I I Common Stock 2008-12-04 4 P 0 200 17.68 A 5446511 I I Common Stock 2008-12-04 4 P 0 200 17.71 A 5446711 I I Common Stock 2008-12-04 4 P 0 400 17.72 A 5447111 I I Common Stock 2008-12-04 4 P 0 600 17.74 A 5447711 I I Common Stock 2008-12-04 4 P 0 700 17.76 A 5448411 I I Common Stock 2008-12-04 4 P 0 700 17.77 A 5449111 I I Common Stock 2008-12-04 4 P 0 200 17.78 A 5449311 I I Common Stock 2008-12-04 4 P 0 600 17.79 A 5449911 I I Common Stock 2008-12-04 4 P 0 1400 17.80 A 5451311 I I Common Stock 2008-12-04 4 P 0 600 17.81 A 5451911 I I Common Stock 2008-12-04 4 P 0 200 17.82 A 5452111 I I Common Stock 2008-12-04 4 P 0 800 17.83 A 5452911 I I Common Stock 2008-12-04 4 P 0 200 17.84 A 5453111 I I Common Stock 2008-12-04 4 P 0 400 17.85 A 5453511 I I Common Stock 2008-12-04 4 P 0 600 17.86 A 5454111 I I Common Stock 2008-12-04 4 P 0 200 17.87 A 5454311 I I Common Stock 2008-12-04 4 P 0 200 17.88 A 5454511 I I Common Stock 2008-12-04 4 P 0 800 17.89 A 5455311 I I Common Stock 2008-12-04 4 P 0 100 17.90 A 5455411 I I Common Stock 2008-12-04 4 P 0 700 17.91 A 5456111 I I Common Stock 2008-12-04 4 P 0 1400 17.92 A 5457511 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