Our knowledge about which prostate cancers are life threatening and which are not is limited. Thus, for ethical, medical, and economic reasons we need to define which patients can be managed by Active Surveillance From 1993 through 1999, men from the Rotterdam section of the European Randomized study of Screening for Prostate Cancer (ERSPC) were screened by two strict protocols, which were based on prostate- specific antigen (PSA), digital rectal examination, and transrectal ultrasound. For this study, men with criteria that reflect current active surveillance studies were selected: those with a biopsy Gleason score ≤3+3 in two or fewer cores, with a PSA density Of the 1,014 prostate cancers detected in the prevalence screen, 293 men (28.9%) met the criteria for active surveillance. Their mean age was 65.7 and the mean PSA level was 4.8ng/ml. Radical prostatectomy was elected by 136 men (46.4%), radiotherapy by 91 (31.1%), and watchful waiting by 64 (21.8%). The mean follow-up was 80.8 months. The eight-year prostate cancer-specific survival was 99.2%; the overall survival was 85.4%. Nineteen men who chose watchful waiting changed to definitive treatment during follow-up. Only three men died of prostate cancer, none of whom were on watchful waiting. Our observations provide preliminary validation of the arbitrary selection criteria for active surveillance.