BACKGROUND: Recently the Korean society has been challenged with the rapid growth of obese population due to the improved socioeconomic status and lifestyle changes over the past decades. Not only has obesity been known as one of major risk factors for various diseases including cardiovascular diseases(e.g. hypertension, coronary heart disease and stroke) and diabetes mellitus, but it has also increased the death from obesity-related diseases. It has been required, however, to establish our own obesity criteria adjusted for Korean since much difference is expected to exist in the degree of obesity between white and Asian people. Therefore, this study was designed to provide with primary data to help establish new criteria through identifying the distribution of Body Mass Index(BMI), and then analysing its relatian with some obesity-related diseases. METHODS: This study calculated BMI and related it to some obesity-related diseases by analysing data from 1995 National Health Interview Surveys, in which a random sample of 5,750 Korean at the age of 15-69 had self-reported their heights, body weights and diagnoses with obesity-related diseases by physicians. Variables under consideration include potential risk factors(e.g. alcohol intakes, smoking, exercise, etc.) as well as demographics of the sample population. RESULTS: Average BMI(kg/m(2)) were 21.6+/- 2.6 for male and 21.7+/-4.8 for female(mean+/-SD), which increased in direct proportion to the increase of age until the age reached the group of 40-59, and then followed by the inverse in its relation with the age at 60 and over. It was revealed, however, that prevalences of obesity-related diseases such as hypertension, diabetes mellitus etc. were the highest among the population group with their BMI of 23.8~35.6. In short, this study identified the proportional relation of BMI with the prevalence of obesity-related diseases. CONCLUSIONS: In this study, the prevalence for hypertension and diabetes mellitus was shown to be higher than the average among population with their BMI of 21.9~238, whose figure is much lower than both 26.4, the value of the 90th percentile proposed in MONICA prot and 25, the current WHO criteria of obesity. However, a Japanese study reported that the health risk began to increase at the BMI of 23 with risks for obesity-related diseases dramatically increased at the BMI of 26-27 and over, and concluded that because Asian has more body fats accumulated within the upper body part compared with the white, the Asian persons are more obese, though less in terms of BMI, than the white. Therefore, future works should be focused on establishing our own criteria for obesity with health risks through determining the association of BMI with prevalence of various diseases in Korea.