The present invention relates to novel polymorphic forms of 8-fluoro-2-{4- [(methylamino)methyl]phenyf}-1,3,4,5-tetrahydro-6H-azepino(5,4,3-cd]indol-6-one;(I), and to processes for their preparation. Such polymorphic forms may be a component of a pharmaceutical composition and may be used to treat a mammalian disease condition mediated by poly(ADP-ribose) polymerase activity including the disease condition such as cancer.