PURPOSE: To determine whether cigarette smoking increases the risk of rheumatoid arthritis among postmenopausal women. SUBJECTS AND METHODS: We followed a cohort of 31 336 women in Iowa who were aged 55 to 69 years in 1986 and who had no history of rheumatoid arthritis. Through 1997, 158 cases of rheumatoid arthritis were identified and validated based on review of medical records and supplementary information provided by physicians. Multivariable Cox proportional hazards regression was used to derive rate ratios (RRs) and 95% confidence intervals (CIs) for the association between cigarette smoking and rheumatoid arthritis. RESULTS: Compared with women who had never smoked, women who were current smokers (RR = 2.0; 95% CI: 1.3 to 2.9) or who had quit 10 years or less before study baseline (RR = 1.8; 95% CI: 1.1 to 3.1) were at increased risk of rheumatoid arthritis, but women who had quit more than 10 years before baseline were not at increased risk (RR = 0.9; 95% CI: 0.5 to 2.6). Both the duration and intensity of smoking were associated with rheumatoid arthritis. Multivariable adjustments for age, marital status, occupation, body mass index, age at menopause, oral contraceptive use, hormone replacement therapy, alcohol use, and coffee consumption did not alter these results. CONCLUSION: These results suggest that abstinence from smoking may reduce the risk of rheumatoid arthritis among postmenopausal women.