187 Background: Whether ethanol intake contributes to prostate cancer (CaP) risk is debated. Although ethanol was found to contribute to increased CaP risk in the Prostate Cancer Prevention Trial, whether ethanol intake impacts CaP risk among men with previous negative biopsies has not been previously assessed. We therefore examined the relationship between ethanol consumption and CaP risk in the REDUCE trial and further sought to determine whether ethanol intake modifies the effect of dutasteride in reducing CaP risk. Methods: This is secondary analyses using data from 6,729 men who had at least one on-study biopsy while participating in the REDUCE trial. Ethanol intake, which was expressed as units (½ pint of beer or 1 glass of wine, etc.) per week, was analyzed as a continuous and three-tiered categorical variable [non-drinker, moderate (≤7 units/week), heavy-drinker (>7 units/week)]. Risks for overall and high-grade (Gleason ≥7 vs. Gleason<7 CaP or biopsy negative) CaP were evaluated using logistic regression adjusting for clinical parameters including dutasteride intake. Test for interaction was used to determine whether the association between dutasteride and CaP risk is influenced by ethanol. Results: Forty-nine percent were moderate-drinkers and 26% were heavy-drinkers. On a continuum, increased ethanol intake was significantly associated with elevated risk for overall (p=0.035) and high-grade CaP (p=0.048). Compared to non-drinkers, heavy drinkers were at increased risk for overall (OR 1.21; 95% CI 1.02-1.43; p=0.03) and high-grade CaP (OR 1.34; 95% CI 1.01-1.78; p=0.04). Risks for overall (p=0.55) and high-grade CaP (p=0.21) were comparable between moderate- and non-drinkers. Dutasteride reduced overall CaP risk (OR 0.73; p<0.001) and ethanol intake did not modify the effect of dutasteride on CaP incidence (p-interaction=0.64). Conclusions: Among low-risk men with at least one prior negative prostate biopsy, heavy ethanol intake is associated with increased risk for overall and high-grade CaP. In contrast to CaP prevention with finasteride, which appears to be inhibited by heavy ethanol intake, consumption of ethanol does not negatively impact CaP prevention with dutasteride.