This study was designed to investigate the relationship between body mass index (BMI) and dietary intake, and the relationship between BMI and plasma lipid levels in Korean adults. This study was conducted from January 1 to December 31 of 1997. It consisted of 3781 subjects (men 2402, women : 1379) with the majority between the ages of 40 and 59. The dietary assessment was based upon a twenty-four-hour food record. Subjects were classified into one of four reference BMI groups : underweight ($leq 20 kg/m^2$), normal (20.1-25.0 kg/$m^2$), overweight (25.1-30.0 kg/$m^2$), and obese (>30 kg/$m^2$). The biochemical assessment included measurements of plasma total cholesterol (TC), HDL-cholesterol (HDL-C), LDL-cholesterol (LDL-C), triglyceride (TG), lipoprotein (a), and plasminogen activator inhibitor-1 (PAI-1). The BMI study showed that 60.5% of the men measured were normal and 32.6% of the men were overweight and/or obese subjects. Sixty-four percent of the women were normal and 20.3% of the women measured were overweight and/o. obese subjects. With respect to the daily energy intake of the men and women subjects, the levels of daily energy intake appeared to increase as values of BMI increased. Men of the overweight group had significantly higher protein, fat and cholesterol intake than those of the normal or the underweight groups. The alcohol intake of the men in the overweight group was also significantly higher than that of the men in the underweight group. With respect to percent energy intake of macronutrients, there was no significant difference between the four BMI groups and percent energy intake for all the subjects in the study. The ratio of percent energy intake of carbohydrates : protein : fat : alcohol of the normal women group was 62 : 17 : 20 : 1, respectively. Women apparently had a higher intake of carbohydrates than men (52 : 17 : 19 : 10). With respect to the levels of plasma TC, LDL-C, TG, and HDL-C, the levels of plasma TC, LDL-C and TC appeared to increase as the values of BMI increased, while the level of HDL-C appeared to decrease as values of BMI increased. Levels of lipoprotein (a) appeared to be inversely related to the values of BMI, and levels of PAI-1 appeared to increase as values of BMI increased. The results of this study demonstrate that there is a relationship between dietary intake and BMI, and that there is a relationship between BMI and blood lipids levels.