Abstract CWR22Rv1 (22Rv1) is an androgen-responsive human prostate carcinoma cell line derived from a primary prostate tumor that expresses mutant (H874Y) androgen receptors (AR) and secretes low levels of prostate specific antigen (PSA). In this study, we examined the effects of various androgens and other steroid hormones on proliferation of 22Rv1 cells, PSA secretion, and transactivation. Incubation of 22Rv1 cells with various concentrations of testosterone resulted in a dose-dependent 50–80% increase in growth over 72 h. PSA release and transactivation of PRE 2-tk-LUC in 22Rv1 cells were stimulated by low concentrations of natural and synthetic androgens (EC 50s = 10 −10 to 10 −9 M) and a broad range of other classes of steroid hormones, albeit with lower potency. Uniform positive immunocytochemical staining was observed in 22Rv1 cell nuclei with mouse monoclonal antibodies to human AR. Competitive binding assays indicated that the mutant AR in 22Rv1 cytosol is more promiscuous than a wild-type AR (ARLBD: rat AR ligand binding domain). Testosterone (10 −8 M)-induced PSA release and transactivation were blocked by both antiandrogens and antiprogestins with IC 50s of 10 −7 to 10 −6 M. At high concentration (10 −6 M), these antagonists showed partial agonist activity in terms of PSA secretion but not transactivation. In conclusion, the mutant AR in 22Rv1 cells binds and responds to low levels of androgens and a wide spectrum of other natural and synthetic steroid hormones, mechanisms proposed to contribute to tumor progression following androgen ablation.