Persons with intellectual disability（ ID） are at significantly greater risk of obesity and physically inactive. However, SpecialOlympics （SO） participants, who are persons with ID, are given the opportunity for year-round sports training and athleticcompetition. The aim of the present study was to describe the prevalence of obesity based on the body mass index（ BMI） inJapanese SO participants with ID, and their exercise habit. The BMI was calculated from the following formula: （body mass,kg） / （body height, m）2. Their exercise habit （duration and frequency of exercise） was evaluated using the questionnaire.The chi-square test was used for statistical analysis. For male subjects, 10% of them were underweight, 70% in the normalrange, and 20 % obese. For female subjects, 6 % of them were underweight, 79 % in the normal range, and 15 % obese. Theprevalence rate of the BMI status in both male and female subjects was similar to the corresponding value in Japanese personswithout ID. The longer duration and higher frequency of exercise were found in the present subjects with ID compared toJapanese general persons without ID. These results suggest that the participation of Japanese persons with ID in SpecialOlympics provides the opportunity of the regular exercise and possibly contributes to prevent obesity.