A mass health examination was performed to assess the glucose tolerance of inhabitants of the island of Ojika, in the Goto islands, Nagasaki prefecture Japan. There were 554 males and 820 females older than 34 years who participated in the mass health examination, a response rates of 42 percent and 52 percent for males and females respectively. Serum glucose levels after overnight fasting and at 2 hours after a 75 gram oral glucose tolerance were used with WHO criteria to classify individuals. Among these subjects, the prevalence of diabetes mellitus increased with age, with a prevalence of diabetes mellitus of around 10 percent in the older subjects. The prevalence for males was higher than that for females. Prevalences of impaired glucose tolerance were roughly in the 15-25 percent range and did not show clear differences among different age groups and sexes. From a questionnaire survey of all island inhabitants, it was considered that the degree of bias of the results was small, if any. The true prevalence for all the inhabitants may be a little larger than the observed prevalence of these subjects.