Bodycomposition measurement is useful in the diagnosis of pathoogy, assessment of disease process and response to treatment in many endoclonologic and metabolic diseases. The Techniques used currently are mostly indirect, often expensive, difficult and time-consuming. A new method for estimation of body composition, infrared interactance, is rapid, safe, noninvasive, and may be useful in research ad clinical studies. Body composition was assessed in 51 children and adolescants with insulin-dependent disbetes mellitus by infrared interactance method using a Futrex 5000A body fat content analyzer. Perentage body fat of pubertal girls was 26.1?.6%, significantly greater than prepubertal girls (17.9%, 0<0.01) and pubertal boys (19.9%, p<0.05), Body fat content was increased through puberty in girls, but not increased in boys. Our data do not explain why body fat of pubertal boys was not increased. There was no significant association of insulin dose and HbA1Clevel with percentage body fat. Thus, we had to attempt measure calorie intake, activity level and diet composition. Our data revealed that dietary carbohydrates any prompt fat deposition, but energy balance does not explain the differences between pubertal girls and boys. In conclusion, Body fat increased through puberty in girls, but the etiology of differences in pubertal girls and boys is not clear, and in view of potential adverse effect of fat depostion of long-term health, further larger case-contolled study will be necessary.