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 0 400 17.64 A 5373042 I I Common Stock 2008-12-04 4 P 0 100 17.65 A 5373142 I I Common Stock 2008-12-04 4 P 0 300 17.67 A 5373442 I I Common Stock 2008-12-04 4 P 0 200 17.68 A 5373642 I I Common Stock 2008-12-04 4 P 0 800 17.69 A 5374442 I I Common Stock 2008-12-04 4 P 0 200 17.73 A 5374642 I I Common Stock 2008-12-04 4 P 0 400 17.74 A 5375042 I I Common Stock 2008-12-04 4 P 0 400 17.75 A 5375442 I I Common Stock 2008-12-04 4 P 0 200 17.76 A 5375642 I I Common Stock 2008-12-04 4 P 0 2300 17.77 A 5377942 I I Common Stock 2008-12-04 4 P 0 400 17.78 A 5378342 I I Common Stock 2008-12-04 4 P 0 2000 17.79 A 5380342 I I Common Stock 2008-12-04 4 P 0 1100 17.80 A 5381442 I I Common Stock 2008-12-04 4 P 0 400 17.81 A 5381842 I I Common Stock 2008-12-04 4 P 0 900 17.82 A 5382742 I I Common Stock 2008-12-04 4 P 0 1000 17.84 A 5383742 I I Common Stock 2008-12-04 4 P 0 200 17.85 A 5383942 I I Common Stock 2008-12-04 4 P 0 700 17.87 A 5384642 I I Common Stock 2008-12-04 4 P 0 200 17.88 A 5384842 I I Common Stock 2008-12-04 4 P 0 2100 17.89 A 5386942 I I Common Stock 2008-12-04 4 P 0 400 17.90 A 5387342 I I Common Stock 2008-12-04 4 P 0 900 17.91 A 5388242 I I Common Stock 2008-12-04 4 P 0 900 17.92 A 5389142 I I Common Stock 2008-12-04 4 P 0 800 17.93 A 5389942 I I Common Stock 2008-12-04 4 P 0 300 17.94 A 5390242 I I Common Stock 2008-12-04 4 P 0 800 17.95 A 5391042 I I Common Stock 2008-12-04 4 P 0 200 17.96 A 5391242 I I Common Stock 2008-12-04 4 P 0 400 17.97 A 5391642 I I Common Stock 2008-12-04 4 P 0 200 17.98 A 5391842 I I Common Stock 2008-12-04 4 P 0 500 17.99 A 5392342 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