The present invention relates to novel polymorphic forms of 8-fluoro-2-{4-[(methylamino)methyl]phenyl}-1,3,4,5-tetrahydro-6H-azepino[5,4,3-cd]indol-6-one, 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.本發明係關於新穎8-氟-2-{4-[(甲基胺基)甲基]苯基}-1,3,4,5-四氫-6H-氮呯并[5,4,3-cd]吲哚-6-酮之多晶形式及其製備方法。該等多晶形式可為醫藥組合物之組份且可用於治療由聚(ADP-核糖)聚合酶活性介導之哺乳動物疾病病狀,包括諸如癌症之疾病病狀。