We investigated the effect of pumpkin-seed supplementation on oxalcrystalluria and urinary composition in 20 boys age 2-7 yr from a hyperendemic area of Ubol province in Thailand. The experiment had four periods: control (before treatment), oxalate supplementation 5mg X kg-1 body wt X day-1, pumpkin-seed or orthophosphate supplementation 60 mg X kg body wt-1 X day-1, and posttreatment. Causal morning and 24-h urines were collected analyzed for crystalluria, pH, calcium, phosphorous, oxalate, creatinine, sodium, potassium, citrate glycosaminoglycans, and pyrophosphate. The results demonstrated that the longer the supplementation period of pumpkin seeds, the better were the results. Pumpkin seeds lowered calcium-oxalate crystal occurrence and calcium level but increased phosphorus, pyrophosphate, glycosaminoglycans, and potassium values in urine as compared with orthophosphate supplementation. Pumpkin seeds provide high phosphorus levels and can be used as a potential agent in lowering the risk of bladder-stone disease.