OBJECTIVE: To analyze the clinical history and evolution of children and adolescents with IH, emphasizing some of their peculiar features. METHODS: We followed 471 patients with IH at an outpatient clinic. Patients were submitted to the following protocol: abdominal X-ray, kidney and urinary tract ultrasonography; urinary ionogram, blood gas and biochemical analyses; 24-hour urine for measurement of calcium and other electrolytes and creatinine; urinalysis, urine culture and phase-contrast microscopy; second morning urine collected after fasting for measurement of calcium and creatinine. RESULTS: At the time of diagnosis, 6% of the patients were infants, 15% pre-school children, 55% school children, and 24% adolescents; 56% of them were boys. Clinical and laboratory findings were: 47% had hematuria and abdominal pain, 31% had isolated hematuria, 14% isolated abdominal pain, and 8% had urinary tract infection, nocturnal enuresis, suprapubic pain or urethralgia, or the frequency/urgency syndrome with urinary incontinence. Hypercalciuria was associated with urolithiasis in 56% of patients. There was association with hyperuricosuria in 18.5% of the cases, and hypocitraturia in 8.5% of the cases. Evolution was poor for 33% of the patients, with recurrence of nephrolithiasis, persistence of hematuria, and abdominal pain. CONCLUSIONS: IH must be diagnosed and treated with criteria in order to reduce consequences such as hematuria, abdominal pain, urinary stone formation and possible bone involvement. Signs and symptoms such as urgency and urinary incontinence, suprapubic pain and nocturnal enuresis may result from renal hyperexcretion of calcium.