Bladder stone is a relatively common disease of childhood in West Sumatra with an incidence of 8.3/100,000 population per year. We have studied 87 cases with a peak age of onset of 2-4 years and a male/female ratio of 12:1. The majority of these are from poor families with a diet low in protein and phosphate. Diarrhoea is common. The composition of the stones is primarily ammonium acid urate. Patients with sterile urine have shown significantly higher levels of urinary ammonia than controls, and only approximately 50% of patients' urine were infected. This is consistent with excretion of a high acid load, due both to an acidogenic rice diet and diarrhoea, combined with a low level of phosphate. This condition was once endemic in Europe but is now confined to a belt of countries from the Balkans through Asia.