The management of 78 children with upper urinary calculi is described. Boys outnumbered girls by a ratio of 2 to 1. Two-thirds of the patients had identifiable metabolic causes, while the remaining third had infected renal lithiasis. In this latter group, all patients had had multiple urologic procedures, urinary infection, and stasis with diversionary and indwelling drainage devices. Contrary to earlier views, idiopathic renal lithiasis with or without hypercalciuria was the most common metabolic form of nephrolithiasis in children. Sixty-seven patients (86 per cent) were followed for an average of 7 1/2 years. With appropriate therapy, stone disease became inactive in 70 per cent of the children. The remaining 30 per cent continued with active disease--5 died of renal failure and 1 has received a renal allograft. Stone formation may be regarded as a solitary complication or one of several manifestations of a large number of underlying disorders. Along with a thorough search for etiologic factors there must be an equally aggressive therapeutic effort. Because the disease is ofter sporadic, careful long-term followup of the patients with active as well as those with inactive stone disease is mandatory.