During 1981-1982, a cohort of elderly Japanese Americans living in Hawaii was recruited for an epidemiologic study of osteoporosis. The male subjects were simultaneously being examined for an epidemiologic study of heart disease. Baseline data collected from both the men and women at a previous heart disease examination were used to compare responders vs nonresponders. The target population for the osteoporosis study consisted of 1685 men and 1594 women. Of these, 1379 men (81.8%) and 1105 women (72.0%) participated in the initial osteoporosis examination. For each sex, nonrespondents were older and had higher systolic blood pressure levels than did the respondents. Male nonresponders had a higher stroke prevalence and more frequent recent use of vasodilator medicine. Female nonresponders had a less frequent history of having ever taken female hormones than did the responders. The responders and nonresponders were reasonably similar in other respects, as indicated by the comparison of more than 40 other variables. This suggests that nonresponse bias is probably not a major influence in exposure-disease associations in this osteoporosis cohort. We believe this is the first published report dealing with nonresponse characteristics in a cohort study of osteoporosis.