The authors report a series of 130 children suffering from urinary lithiasis (essentially between the age of 4 to 6 years) and particularly in boys (2.5 to 1). There were 108 cases of reno-ureteric lithiasis as against 23 vesico-urethral. In 69 cases, pyelocalyceal lithiasis predominated. Thirty per cent of the children had bilateral lithiasis, and 19% of all cases of lithiasis were staghorn calculi. Presenting symptoms : haematuria, diffuse abdominal pain, anuria (6 cases), complete urinary retention (5 cases). Study of these cases failed to indicate whether obstruction of the upper urinary tract (14%) or infection (27%) was the cause or the effect of the lithiasis. Particularly notable were 8 cases of cystinuria (6%), 1 of glycinuria, 1 of hyperoxaluria and 7 of hypercalciuria. At least in Spain, lithiasis in children would appear to be essentially idiopathic. However, 40% of these cases of lithiasis were secondary to obstruction of the excretory tract and/or urinary infection. All types of entero-uroplasty were lithogenic (6 cases). 32% of the children had a proteus infection. Treatment : 14 children were treated medically as against 125 surgically. 70% are free of any recurrence. 7% have a residual lithiasis. The rarity of recurrences and the quality of the results obtained indicate that complete surgical treatment represents the essential feature of the treatment of urinary lithiasis in children.