Cells cultured from human urogenital cancer and other cancers as well as cells from noncancerous tissues were examined by immunofluorescent staining with antibodies to T-antigens and capsid antigens of papovaviruses BK virus (BKV), JC virus, and simian virus 40(SV40), and to capsid antigens of herpes simplex virus types 1 and 2 and human cytomegalovirus (CMV). Cells from early passage cultures of 123 primary tissues and from 14 continuous lines derived from transitional or renal cell carcinoma were tested. None of the cell preparations was specifically stained with any of the antisera. A serologic comparison of patients with bladder cancer, patients with prostate cancer, and normal control groups of BKV hemagglutination-inhibiting and SV40-neutralizing antibodies showed no differences among the 3 groups. None of the sera in the 3 groups had SV40 or BKV T-antibodies. In tests of supernatants of 35 primary cultures for presence of virus, a single isolation, that of a cytomegalovirus, was made. The study revealed no evidence that infection with papovaviruses of the SV40-polyoma subgroup has any part in the production of bladder and prostate cancer.