Previously, we examined the expiratory reserve volume (ERV) of the lungs as a function of percentage body fat in an adult population (age range 18-58 years). A negative correlation resulted when ERV (expressed as a percentage of vital capacity, (ERV/VC) x 100) was regressed on percentage fat for both sexes. In the present study, similar comparisons were made for 33 pre-pubertal boys and girls (aged 7-12.5 years).