Objectives. To assess the relation between the percentage of body fat, the Body Mass Index and the abdominal perimeter in a population of school students who live at a moderate altitude. Materials and methods. A cross-sectional study was conducted, for which 394 boys and 405 girls between 6 and 11 years of age were selected using a probabilistic method. All the school students chosen were middle class children who lived in the urban area of Arequipa, Peru, located at a moderate altitude (2320m above sea level). The percentage of fat, the Body Mass Index and the abdominal perimeter were assessed. Results. There was a moderate correlation between the percentage of fat and the abdominal perimeter in boys (0.59) and girls (0.68). Lower figures were obtained between the percentage of fat and the Body Mass Index in boys (0.56) and girls (0.66). A connection among the categories of fat percentage (%F) and the abdominal perimeter (p<0.05) was observed; yet, there was no connection between the %F and the Body Mass Index (p>0.05). Conclusions. The abdominal perimeter has a moderate correlation with the percentage of body fat and can be used as an indicator of adiposity in the mid-section of the body of children who live in Arequipa (Peru) at a moderate altitude.