OBJECTIVE: To evaluate whether blood transfusion, alcohol use, or anthropometric characteristics are risk factors for rheumatoid arthritis (RA) in older women. METHODS: These factors were evaluated in a prospective cohort study that was initiated in 1986, and included 31,336 women aged 55-69 years without a history of RA. Risk factor data were self-reported using a mailed questionnaire. Through 1997, 158 cases of RA meeting at least 4 of 7 American College of Rheumatology criteria were identified and validated by medical record review. The relative risk (RR) and 95% confidence interval (CI) were used as the measure of association, and were adjusted for the potential confounding effects of age, marital status, smoking history, age at menopause, and use of estrogen replacement therapy. RESULTS: History of blood transfusion was inversely associated with RA (multivariate RR = 0.72; 95% CI 0.48-1.08), and this association was stronger for rheumatoid factor (RF) positive disease (RR = 0.59; 95% CI 0.35-1.00). There were no associations for use of medications for hyper- or hypothyroidism or adult onset diabetes. Anthropometric factors (height, weight, body mass index, body fat distribution), leisure time physical activity, and alcohol use were not associated with risk of RA. CONCLUSION: A history of blood transfusion was inversely associated with RA, particularly RF positive RA. Anthropometric factors, physical activity, and alcohol use did not influence the risk of RA in this cohort of older women.