In 56 patients with simple obesity blood glucose and insulin levels were assessed under fasting conditions and after oral glucose tolerance test. Besides, several lipid metabolism parameters like triglycerides, HDL--and LDL--cholesterol were estimated, too. Direct relationship was found between the impairment of glucose tolerance and the duration of obesity and the overweight. Obese persons with higher overweight and an average duration of obesity exhibited fasting hyperinsulinemia. Irrespective of the overweight magnitude and the degree of glucose tolerance impairment a more pronounced insulin reaction to glucose was observed. The same was found in the groups of persons with the history of obesity not exceeding 15 years. Moreover, in the group of obese persons with normal glucose tolerance, in those with overweight reaching 70% and with short and moderate duration of. Fasting obese hyperinsulinemic persons showed reduced concentration of HDL--obesity the levels of triglycerides were found to be elevated.