The Tecumseh Community Health Study provides an opportunity to investigate the role of obesity in the etiology of osteoarthritis. This longitudinal study, conducted in Tecumseh, Michigan, began in 1962 with baseline examinations of clinical, biochemical, and radiologic characteristics. A 1985 reexamination of the cohort characterized osteoarthritis status in 1,276 participants, 588 males and 688 females, who were aged 50-74 years at this follow-up. Baseline obesity, as measured by an index of relative weight, was found to be significantly associated with the 23-year incidence of osteoarthritis of the hands among subjects disease free at baseline. Greater baseline relative weight was also associated with greater subsequent severity of osteoarthritis of the hands. The difference between baseline and follow-up weight values was not significantly associated with the incidence of osteoarthritis of the hands. Furthermore, there was no evidence that development of osteoarthritis subsequently led to increased incidence of obesity.