During the last six years 400 children with urolithiasis underwent a six weeks rehabilitation treatment in a specialized children's sanitorium for renal diseases. The clinical picture, course of the disease, etiology, complications and therapy are analyzed and discussed. Urolithiasis is surprisingly common in girls; it occurs commonly not until school age and recurrence occurs in one-fourth of the children. The importance of stone analysis for the therapy is outlined and the necessity of conservative renal surgery is emphasized.