A total of 61 patients, less than 70 years old at diagnosis, with clinical stage T1-2, NX, M0, cytologically well or moderately differentiated prostate adenocarcinoma was prospectively included in a surveillance study. Median patient age was 63 years (range 38 to 69 years). Mean followup was 96 +/- 24 months. The probability of local progression to stage T3 disease after 5 and 10 years was 49 and 72%, respectively. The probability of metastases developing after 5 and 10 years was 8 and 23%, respectively. The probability of dying of prostate adenocarcinoma was 2 and 8%, respectively. Moderately differentiated cancer progressed locally significantly faster than well differentiated disease. The relative number of patients who had metastases or died of prostate adenocarcinoma found in our study was comparable to the relative numbers reported after radical prostatectomy and radiation therapy. Therefore, deferred therapy may be an alternative to active therapy in patients with clinically localized prostate adenocarcinoma and with a life expectancy of less than 10 years.