Physical activity has been inconsistently related to total prostate cancer and few studies have examined whether this association varies by disease aggressiveness. We examined physical activity in relation to total, advanced, and fatal prostate cancer in the NIH-AARP Diet and Health Study. At baseline (1995-1996), 293,902 men ages 50 to 71 years completed a questionnaire inquiring about current frequency of vigorous exercise of at least 20 min of duration, as well as frequency of exercise during adolescence (ages 15-18). We used proportional hazards regression to calculate multivariate relative risks (RR) and 95% confidence intervals (95% CI). During up to 8.2 years of follow-up, 17,872 prostate cancer cases were identified, including 1,942 advanced and 513 fatal cases. Comparing frequent (5+ times per week) versus infrequent (less than once per week) vigorous exercise, exercise at baseline was not associated with risk of total prostate cancer (RR, 1.01; 95% CI, 0.96-1.07; Ptrend = 0.78), advanced prostate cancer (RR, 1.14; 95% CI, 0.97-1.33; Ptrend = 0.25), or fatal prostate cancer (RR, 0.90; 95% CI, 0.67-1.20; P trend = 0.12). Increasing level of vigorous exercise during adolescence was associated with a small 3% reduction in total prostate cancer risk (frequent versus infrequent exercise during adolescence: RR, 0.97; 95% CI, 0.91-1.03; Ptrend = 0.03) but was not associated with risk of advanced prostate cancer (RR, 0.95; 95% CI, 0.78-1.14; Ptrend = 0.18) or fatal prostate cancer (RR, 0.96; 95% CI, 0.67-1.36; Ptrend = 0.99). Neither vigorous exercise at baseline nor exercise during adolescence was related to risk of total, advanced, or fatal prostate cancer in this large prospective cohort.