Adenocarcinoma of the prostate occasionally is discovered incidentally in the enucleated gland at open prostatic adenectomy for benign disease. Among 468 men who underwent open prostatic adenectomy, unsuspected adenocarcinoma of the prostate was found on pathological examination in 28 (6.0 per cent). The tumors were stage A1 in 14 patients and stage A2 in 14. Careful tissue review resulted in reassigning 5 cases from stage A1 to stage A2. At a mean followup of 10.6 years disease progression had occurred in 4 patients with stage A2 disease. When stage A adenocarcinoma is discovered after open prostatectomy we recommend careful review of the surgical specimen for accurate staging, and adjuvant therapy for all patients with stage A2 disease an for younger patients (less than 65 years old) with stage A1 disease who have favorable life expectancies.