The purpose of this study is to analyze the age and gender variability of body composition in children and adolescents by using bioelectrical impedance-metric method. We transversally examined 738 boys and 753 girls, aged 10-17 years, from different schools in Plovdiv (Bulgaria) in 2008. Using the apparatus ABC-01 Medas, we measured the features of body composition of each child. The data were statistically processed. The results show an increase in the absolute amounts of adiposeand fat-free tissue in both sexes with age advancing. After the age of 11, fat mass was significantly more in body composition of girls, while the fat-free one - in body composition of boys. In the period from 10 to 14 years, the differences between the sexes in the active cell mass are insignificant, and then the values of this feature begin to rise in boys. At the age 12-13 there were significant intersexual differences in respect with the active resistance and phase angle. In both sexes, reactance varies in weak borders and irregularly.
