OBJECTIVE To evaluate the short-term outcomes of the prospective international Prostate Cancer Research International: Active Surveillance ('PRIAS') study (Dutch Trial Register NTR1718), as active surveillance (AS) for early prostate cancer might provide a partial solution to the current overtreatment dilemma in this disease. PATIENTS AND METHODS The first 500 (of > 950) participants with asymptomatic T1c/T2 prostate cancer, with a prostate-specific antigen (PSA) level of < 10.0 ng/mL, a PSA density of < 0.2 ng/mL/mL, a Gleason score of < 3 + 3 = 6, and one or two positive biopsy cores, were analysed. The follow-up protocol consisted of frequent PSA measurements, digital rectal examinations, and standard repeat biopsies (the first after 1 year). The primary outcome is survival free of active therapy; the secondary endpoints are reasons for stopping AS, findings in 1-year repeat biopsies, and outcomes after radical prostatectomy (RP). RESULTS Patients were included between December 2006 and July 2008. The median (25-75th percentile) follow-up after diagnosis was 1.02 (0.6-1.5) years. The 2-year survival rate free from active therapy was 73%. Of the 82 men who changed to active therapy during the follow-up, 68 (83%) did so based on the protocol. Of the 261 repeat biopsies available for analysis, 90 (34%) showed no cancer, while 57 (22%) showed a Gleason score of > 6 or more than two positive biopsy cores. There was a relatively unfavourable PSA doubling time of 0-10 years in 53% (102/194) and 62% (33/53) of men with favourable and unfavourable re-biopsy results, respectively. After RP, four of 24 (17%) men had T3 disease and 12 (50%) had a Gleason score of > 6. CONCLUSION AS seems feasible, but mortality outcomes are unknown. A strict follow-up protocol including standard 1-year repeat biopsies resulted in a quarter of men stopping AS after 2 years.