We examined the effect of body weight change on the modification of atherogenic risk factors in 296 middle-aged obese male office workers without medication for hypertension, dyslipidemia, hyperuricemia or diabetes mellitus. During a 1-year education program, 39.2% of the participants could reduce their weight, and the percentage of those who lost 2 kg or more was only 17.7%. Concomitant with the decrease of weight, however, the levels of systolic and diastolic blood pressures, total cholesterol, triglyceride, uric acid and hemoglobin _1c and the ratio of total cholesterol to high-density lipoprotein (HDL) cholesterol decreased significantly, whereas the HDL cholesterol level increased significantly. In a multivariate regression analysis, in addition to the initial risk-factor level, weight change was an important factor determining the changes in atherogenic risk factors. Changes in alcohol consumption were significantly associated with the changes in systolic blood pressure and HDL cholesterol levels. Changes in cigarettes smoking also showed significant associations with the changes in triglyceride level and the ratio of total cholesterol to HDL cholesterol. These results suggest that although the education program for controlling weight may have limited success, weight reduction exhibits beneficial changes in the atherogenic risk-factor profile in middle-aged obese men.