Study objective: To examine the association of cigarette smoking and alcohol consumption with hospital presentation of ARDS in a wed-defined, multiethnic population. Design: Retrospective cohort study. Setting: Health maintenance organization in Northern California, Participants: A total of 121,012 health plan subscribers (54.2% women), aged 25 to 89 years. Outcome measure: Hospital presentation of ARDS (validated by medical chart review) from baseline in 1979 to 1985 through the end of 1993 (median, 9.9 years). Results: There were 56 cases of ARDS (33 in men, 23 in women). The case fatality rate was 39% in both genders. ARDS was independently, related to increasing age (rate ratio of 10 years, 1.38; 95% confidence internal [CI], 1.12 to 1.71), to current smoking of < 20 cigarettes/d (rate ratio vs never cigarette smokers, 2.85; 95% CI, 1.23 to 6,60), and to current cigarette smoking of greater than or equal to 20 cigarettes/d (rate ratio vs never smokers, 4.59; 95% CI, 2,13 to 9,88), No association was observed between alcohol consumption and ARDS. Conclusions: The results of this study suggest a relationship (with evidence of dose-response effect) between cigarette smoking and ARDS, Assuming a causal relationship, approximately 50% of ARDS cases were attributable to cigarette smoking.