X0306 4 2013-06-25 0 0001528129 Laredo Petroleum Holdings, Inc. LPI 0001528258 Warburg Pincus Private Equity X O&G, L.P. C/O WARBURG PINCUS & CO. 450 LEXINGTON AVENUE NEW YORK NY 10017 1 0 1 0 0001451560 Warburg Pincus X Partners, L.P. C/O WARBURG PINCUS & CO. 450 LEXINGTON AVENUE NEW YORK NY 10017 1 0 1 0 0001414561 Warburg Pincus X, L.P. C/O WARBURG PINCUS & CO. 450 LEXINGTON AVENUE NEW YORK NY 10017 1 0 1 0 0001414564 Warburg Pincus X LLC C/O WARBURG PINCUS & CO. 450 LEXINGTON AVENUE NEW YORK NY 10017 1 0 1 0 0001322709 Warburg Pincus Partners LLC C/O WARBURG PINCUS & CO. 450 LEXINGTON AVENUE NEW YORK NY 10017 1 0 1 0 0000929408 WARBURG PINCUS & CO. C/O WARBURG PINCUS & CO. 450 LEXINGTON AVENUE NEW YORK NY 10017 1 0 1 0 0001162870 WARBURG PINCUS LLC C/O WARBURG PINCUS & CO. 450 LEXINGTON AVENUE NEW YORK NY 10017 0 0 1 0 0001239318 KAYE CHARLES R C/O WARBURG PINCUS & CO. 450 LEXINGTON AVENUE NEW YORK NY 10017 0 0 1 0 0001220638 Landy Joseph P. C/O WARBURG PINCUS & CO. 450 LEXINGTON AVENUE NEW YORK NY 10017 0 0 1 0 Common Stock, par value $0.01 per share (''Common Stock'') 2013-06-25 4 J 0 755278 0 D 17016375 D See Exhibit 99.1; Note 1. See Exhibit 99.1; Note 2. *** The Power of Attorney given by Warburg Pincus & Co. was previously filed with the U.S. Securities & Exchange Commission on January 15, 2013 as an exhibit to a statement on Schedule 13D/A filed by Warburg Pincus Private Equity X, L.P. with respect to Talon Therapeutics, Inc. and is hereby incorporated by reference. Exhibit List: Exhibit 99.1 - Explanation of Responses Exhibit 99.2 - Joint Filer Information Exhibit 99.3 - Joint Filers' Signatures /s/ Scott A. Arenare, Attorney-in-Fact of Warburg Pincus & Co., as Managing Member of Warburg Pincus Partners LLC, as Sole Member of Warburg Pincus X LLC, as GP of Warburg Pincus X, L.P., as GP of Warburg Pincus Private Equity X O&G, L.P. 2013-06-26