We examined the prospective relationship between metacarpal bone mass and osteoarthritis (OA) of the hand, using incidence data from the historical cohort in the Tecumseh Community Health Study (Tecumseh, MI). Women were examined for radiographic evidence of OA and for bone mass twice, 20-23 years apart (1962-1965 and 1985; 683 subjects with an age range of 55-74 in 1985). Two measures of OA were evaluated: the highest score assigned to any of the 32 wrist/hand joints, and the sum of scores for all wrist/hand joints. After adjustment for age, women who were classified as having OA (by either measure of OA) in 1985 were more likely to have more cortical area at baseline, which indicates greater bone mass. Women who developed OA in the 23-year period were more likely to experience a significantly greater widening of the medullary cavity over time, an indicator of increased bone resorption. Women with increasing levels of OA involvement also had an increased likelihood of greater cortical area loss. We conclude that women who later developed OA were more likely to have higher baseline bone mass than women who did not develop OA, but these women also had a greater likelihood of bone loss over time.