The blood pressure, electrocardiographic findings and serum total cholesterol of Tongans, characterized by extreme obesity, were compared with those of Japanese employees of a trading firm in Tokyo. The prevalence of cardiovascular diseases in Tongans as far as assessed by these measurements was rather low for their excessive obesity. It is unclear whether the relatively low prevalence rate of cardiovascular diseases among the Tongans is due to genetic factors which might be considered an ethnological difference, or to environmental factors. Reducing weight is very difficult for many obese people. Accordingly, if "healthy obesity" exists, elucidation of its mechanism will be glad tidings for obese persons. However, the most prevalent diseases among the Tongans were the same as those of the developing countries. Consequently, imitating the Tongan lifestyle does not necessarily assure the longevity of obese persons of developed nations, although it may decrease the risk of the cardiovascular diseases.