Abstract: Background and Objectives: Most students use backpacks to carry their school supplies. Backpack carriage affects posture, physiological costs and physical performance. Limited literature concerning the effects of backpack load effect on pulmonary capacities of schoolchildren has been reported. The purpose of this study was to determine the effects of different backpack weights on pulmonary capacities of schoolchildren. Methods 30 healthy subjects participated in this study. Subjects, completed two 20min exercise stages for each backpack condition [no backpack (0%) and backpack weighing 5, 10 or 15 % of body weight. Forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1) and (FEV1/FVC) for each condition were measured in 30. Results The main effect of load was found to be significant for FVC, FEV1 and FEV1/FVC. Restrictive effects on the pulmonary function due to backpack carriage were determined. Conclusions: Carrying a backpack with weights generally decreased lung capacity is elementary school students. Obviously carrying backpacks heavier more serious consequences will follow appropriate strategies should therefore carry a backpack to remove the Iranian elementary school students.