OBJECTIVES To review the outcome in patients with clinically localized prostate cancer managed conservatively. METHODS A total of 122 patients with palpable, clinically localized, low-grade prostate cancer diagnosed from 1978 to 1982 at the Karolinska Hospital, Stockholm, Sweden, were prospectively followed in a surveillance protocol followed by treatment when the tumor progressed with symptoms. RESULTS All patients but one had been observed for 10 years or more. No antitumoral therapy had been given to 58 (48%) patients at follow-up or before death. The chance of being untreated 5 and 10 years after diagnosis, if still alive, was 71% and 43%, respectively. The actual disease-specific survival rate at 10 years was 90%. Of the patients with a possible observation period of 15 years or more, 25% died of prostate cancer (ie, an actual disease-specific survival of 75%). Using a survival plot, the projected disease-specific survival rate at 15 years was 62%. The cumulative incidence of death from prostate cancer increased with possible observation time up to 15 years. CONCLUSIONS Our data are mature up to 10 years of observation and, based on these data, deferred treatment is a valid option for patients with clinically localized low-grade prostate cancer with a life expectancy of 10 years or less. The data are not definitive beyond 10 years and firm conclusions will be speculative, but our findings indicate that there probably is room for efficacious local treatment in patients with localized prostate cancer and a life expectancy longer than 10 years.