Study objective: This study evaluated the relation between self-reported marijuana use and 3-year incidence of injury. Methods: We conducted a retrospective cohort study of adult Kaiser Permanente medical Care Program members who underwent multiphasic health examinations between 1979 and 1986 (n=4,462). Injury-related outpatient visits, hospitalizations, and fatalities within 3 years of examination were determined. Results: Outpatient injury events totaled 2,524; 1,611 participants (36%) had at least 1 injury-related outpatient visit. Injury-related hospitalizations (n=22) and fatalities (n=3) were rare. Among men, there was no consistent relation between marijuana use and injury incidence for either former users (rate ratio, 1.15; 95% confidence interval [CI], .97 to 1.36) or current users (rate ratio, 0.97; 95% CI, 81 to 1.17), compared with those who had never used marijuana. Among women, former and current users showed little difference in their rate of later injury compared with never users; the rate ratios were 1.05 (95% CI, 1.00 to 1.44), respectively. No statistically significant associations were noted between marijuana use and cause-specific injury incidence in men or women. Conclusion: Among members of a health maintenance organization, self- reported marijuana use in adult men or women was not associated with outpatient injury within 3 years of marijuana use ascertainment.