A series of 59 consecutive cases of urinary calculi in childhood is presented, being acquired from one local area (Bristol). These children were treated from 1950 to 1973. The peak presentation was in the 2nd and 3rd year of life, with a secondary peak in the 10th year. Anatomical (39%), metabolic (8.5%) or primary infective abnormalities (29%) were demonstrable, but 22% had to be left in an unsatisfactory "idiopathic classification''. The overall recurrence rate of 7% was reduced to 3.5% when those patients with cystinuria were excluded. The local water supply areas have been studied and a tentative association is suggested between patients and their environment when they live in an area where the water is not only hard but also alkaline (pHgreater than 8).