8-Fluorophthalazin-1(2h)-one compounds of Formula II where one or two of X1, X2, and X3 are N, are provided, including stereoisomers, tautomers, and pharmaceutically acceptable salts thereof, useful for inhibiting Btk kinase, and for treating immune disorders such as inflammation mediated by Btk kinase. Methods of using compounds of Formula II for in vitro, in situ, and in vivo diagnosis, and treatment of such disorders in mammalian cells, or associated pathological conditions, are disclosed.