There is a significant difference in survival of patients, with stages A1 and A2 prostatic adenocarcinoma. Therefore, it is important to distinguish focal occult adenocarcinoma from diffuse occult adenocarcinoma. However, that may be impossible from a single transurethral resection of the prostate. This study was designed to determine if repeat transurethral biopsy would be helpful in defining the extent of stage A disease. Between January 1970 and January 1976, 27 of 6) patients with stage A adenocarcinoma of the prostate were selected for repeat transurethral biopsy of the prostate 3 months after the initial diagnosis. All 27 patients had a focus or focal adenocarcinoma of the prostate at the initial resection. Seven patients (26 per cent) were found to have significant residual tumor at repeat resection and were reclassified as stage A2. Three patients were found to, have a single focus of adenocarcinoma on repeat biopsy. Thus, 37 per cent of the study group of patients had residual carcinoma after initial diagnosis by transurethral resection. Repeat transurethral biopsy is helpful in defining the extent of stage A disease and formulating a rational plan of therapy.