Results from epidemiologic studies of physical activity and ovarian cancer have been inconsistent, with 2 prospective studies reporting a modest positive association. We evaluated this relationship in a population-based case-control study conducted in Massachusetts and Wisconsin. Incident cases diagnosed between 1991 and 1994 were identified through statewide tumor registries. Community controls were selected randomly from lists of licensed drivers and Medicare recipients. Participation in moderate and vigorous recreational physical activity at age 12, age 20 and 5 years prior to diagnosis was assessed by telephone interview. Data were available for 327 cases and 3,129 controls. Results were adjusted for age, parity and other ovarian cancer risk factors. Total and vigorous physical activity were not associated with a substantial decrease in ovarian cancer risk at any age. The relative risk (RR) for women reporting ≥ 7 vs. 0 hr/week of recent vigorous activity was 0.85 [95% confidence interval (CI) = 0.39–1.86; p for trend = 0.31]. When metabolic equivalent task (MET) hours of activity were estimated, only women in the highest category had any reduction in risk (RR for > 42 MET-hours/week at the reference age = 0.70; 95% CI = 0.36–1.35; p for trend = 0.41). Overall, our results provide only limited support for an inverse association between recreational physical activity and risk of ovarian cancer. © 2002 Wiley-Liss, Inc.