Inborn hypouricemia due to isolated renal tubular defect is a rare disorder. Thus far eight documented families with this condition have been reported. In reviewing the data on these families, hyperuricosuria was found to be a constant associate of the hypouricemia, and hypercalciuria, mainly of the absorptive type, was frequently associated. Urolithiasis appears to be common. The mode of inheritance of this hypouricemia was autosomal, probably recessive. The magnitude of renal urate clearance and the effects on it of probenecid and pyrazinamide suggest the inborn renal hypouricemia to be of two types, due to defective re-secretory tubular urate reabsorption and to total defective tubular urate reabsorption. The question of the renal tubular abnormality for urate transport being the primary defect or secondary to an abnormal metabolite is discussed.