192 Background: Routine screening for prostate cancer (CaP) was first advocated in 1993 in the US. Opponents of screening argue that the implementation of routine screening has not resulted in a meaningful improvement in survival. Since we are essentially unable to cure metastatic disease, the best measure of the efficacy of screening may not be overall survival but instead its ability to lessen the metastatic disease burden of the screened population. We assess the effect of screening on this endpoint. Methods: From 1986-1996, 1,721 patients with CaP were definitively treated with radical prostatectomy (RP) or radiotherapy (RT) at our institution. The cohort was divided into a pre screening era group (1986-1992; PRE, n=575) and a post screening era group (1993-1996; POST, n=1,146). Due to the potential for an imbalance in follow up time between the two groups, all patients were censored at ten years. Kaplan- Meier analysis was used to calculate the ten year metastases free survival rates (MFSR). Cox proportional hazards regression was used to examine if screening era along with disease, treatment, and follow-up characteristics was associated with an increased risk of developing metastatic disease. Results: The median follow up for all patients was 10 yrs (range: 0.1-10), 9.6 yrs (range: 0.1-10) for PRE patients, and 10 yrs (range: 0.1-10) for POST patients. The distribution by NCCN risk classification for the PRE patients was 44% high risk (H), 21% intermediate risk (I) and 28% low risk (L) vs. 36% H, 27% I, and 37% L for the POST patients (p < 0.0001). Within 10 years of treatment, 13% of all patients had developed metastatic disease. The 10 year MFSR for high risk PRE vs POST patients was 58% vs. 82% (p < 0.0001), 79% vs. 93% for I (p < 0.0001), and 90% vs. 98% (p = 0.0001) for L patients. On multivariable analysis, screening era (p < 0.0001, HR = 4.6, 95% CI = 3.4-6.1), T-stage, biopsy Gleason score, and post-treatment PSA testing frequency were significant. Conclusions: Screening for CaP results in a significant decrease in the risk of a patient developing metastatic disease within 10 years of treatment even after controlling for severity of disease. This risk reduction may yield improved quality of life and a cost savings to the medical care system. No significant financial relationships to disclose.