The natural history of early prostatic cancer has been evaluated in 223 patients with localized (T0-2, NX, M0), newly diagnosed, untreated prostatic cancer in a population-based study. No initial treatment was given and after an observation time of 66-150 months, 73 patients (33%) have progressed (25 with metastases) and 109 died but only 17 of prostatic cancer. Cumulative progression-free survival after 5 and 10 years was 73.1% and 64.3% respectively. Observed survival after 5 and 10 years was 67.3% and 44.1% respectively and the corresponding corrected survival 93.8% and 88.7%. Fifty-eight of the 223 patients filled the present criteria for radical prostatectomy. With only hormonal manipulation after symptomatic progression the corrected survival was very high, 98.0% after 5 years and 89.1% after 10 years among these 58 patients. As a result of this study a randomized trial comparing deferred treatment with radical prostatectomy in this group of patients has been started in Finland and Sweden.