A study of the effect of obesity on glucose tolerance in a Polynesian population (Western Samoa) has not shown a consistent relationship between the two. Although there was a trend for increasing age-standardized prevalence of impaired glucose tolerance and diabetes mellitus with increasing body mass index in males, no such trend was observed in females. The impressive differences in prevalence of abnormal glucose tolerance between rural and urban groups was altered little by adjusting for differences in distribution of body mass index. Environmental factors, such as diet, physical activity, and stress, acting independently of adiposity must have contributed significantly to the observed rural/urban differences in prevalence of abnormal glucose tolerance in Western Samoans.