UNLABELLED: This cross-sectional study investigated the use of schoolbags and the prevalence of musculoskeletal symptoms among a sample of 307 Iranian primary school children aged 7-12 years. The average load carried by the children was 2.9 kg (representing on average 10.1% of the child's body weight). Most children chose to carry the schoolbag across two shoulders, although significant numbers also carried it on one shoulder or in the hand. Although the amount of load carried by school children was within the currently suggested load limit of 10% to 15% of the child's body weight, the prevalence of musculoskeletal problems was very high among the study population. Multiple logistic regression models indicated that the method of carrying the schoolbag was significantly associated with hand/wrist and shoulder symptoms, and that the time spent carrying a schoolbag was associated with hand/wrist and upper back symptoms. Schoolbag weight (expressed as a percentage of body weight) was only associated with hand/wrist symptoms. The results suggest that the current recommended weight limit may not be appropriate for school children in primary school, and that guidelines ought to consider factors other than relative schoolbag weight that influence the use of schoolbags among this age group. PRACTITIONER SUMMARY: The carrying of schoolbags by primary school children and their musculoskeletal symptoms were investigated. The results provide evidence that the current weight limit may not be appropriate for younger school children, and that such guidelines should consider a broader combination of the factors that influence the use of schoolbags.