An 8-year-old boy who had suffered from recurrent stone formation since the age of 4 years, was admitted as an emergency due to anuria for a half day on November 20, 1986. Kidney-ureter-bladder film showed that the urethra was obstructed by a stone, and emergent cystoscopy was performed to remove it. He is the product of consanguinous marriage, his parents being first cousins. There was no family history of renal stone. Laboratory investigations showed hypokalemic, hyperchloremic metabolic acidosis. The ammonium chloride loading test revealed inability to acidify the urine and a markedly decreased excretion of titrable hydrogen ion and ammonium ion in the urine. These results indicate that this is a case of Type I renal tubular acidosis. His 24-hour urinary excretion of oxalate and glyoxylate were also markedly increased. There were no underlying causes leading to the development of secondary hyperoxaluria. These results also establish the diagnosis of Type I primary hyperoxaluria. The patient then received regimens of Polycitra 1ml/kg/day and Vitamin B6 50mg/day for 4 months. However, urinary stone developed again in this patient 4 months later. To our knowledge, Type I primary hyperoxaluria in association with Type I renal tubular acidosis has not been previously reported.