An attempt was made to classify persons with simple obesity from the viewpoint of health education. Subjects of the study were 1,278 male workers in a financing company who underwent health examination. At the time of health examinations, questionnaire survey concerning their life styles was carried out on all the subjects. The obese group consisted of 127 subjects whose obesity indices were over 15% and the control group consisted of 342 subjects whose obesity indices ranged from -5 to 5%. Subjects in the obese group were classified into four clusters based on cluster analysis using five life-style parameters; that is, frequency of taking breakfast, frequency of taking staple food, drinking habits, smoking habits, and frequency of exercise. The first cluster (N = 10) included inactive persons, the second cluster (N = 46) non smokers, the third cluster (N = 39) smokers and heavy drinkers, and the fourth cluster (N = 32) smokers and non-drinkers. Comparison of the four clusters of obese persons with the control group revealed the following findings: 1) All the four clusters had significantly high frequencies of abnormal values of triglyceride (TG) and fasting blood sugar (FBS). 2) The first cluster had significantly high frequencies of abnormal values of glutamic oxalacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT). 3) The second cluster had significantly high frequencies of abnormal values of systolic and diastolic blood pressure, total cholesterol, TG, FBS, uric acid, GOT, GPT and gamma glutamyl transferase (GGT).(ABSTRACT TRUNCATED AT 250 WORDS)