X0203 3 2011-01-28 0 0001084554 LIGHTBRIDGE Corp LTBR 0001044321 MARXE AUSTIN W & GREENHOUSE DAVID M C/O SPECIAL SITUATIONS FUNDS 527 MADISON AVENUE, SUITE 2600 NEW YORK NY 10022 0 0 1 0 Common Stock 1223392 I By Limited Partnership Warrant 9 2011-01-28 2017-07-28 Common Stock 454546 I By Limited Partnership This is a joint filing by Austin W. Marxe (Marxe) and David M. Greenhouse (Greenhouse). They share voting and investment control over all securities owned by Special Situations Fund III QP, L.P. (QP), Special Situations Cayman Fund, L.P. (Cayman) and Special Situations Private Equity Fund, L.P. (PE). 764,932 shares of Common Stock are held by QP, 254,977 shares of Common Stock are held by Cayman, 203,983 shares of Common Stock are held by PE. The interest of Marxe and Greenhouse in the shares of Common Stock owned by QP, Cayman, PE and DG is limited to the extent of his pecuniary interest. This is a joint filing by Austin W. Marxe (Marxe) and David M. Greenhouse (Greenhouse). They share voting and investment control over all securities owned by Special Situations Fund III QP, L.P (QP), Special Situations Cayman Fund, L.P. (Cayman) and Special Situations Private Equity Fund, LP (PE). 284,091 Warrants are owned by QP, 94,697 Warrants are owned by Cayman and 75,758 Warrants are owned by PE. The interest of Marxe and Greenhouse in the shares of Warrants owned by QP, Cayman and PE are limited to the extent of his pecuniary interest. Austin Marxe 2011-01-28 David Greenhouse 2011-01-28