For the last 20 years, 11 patients with clinicopathologic diagnosis of nephronopththisis or medullary cystic disease, have been studied at the Nephrology Department of the Hospital Infantil de México. The initial manifestations took place at ages from 3 to 12 years and consisted of polyuria and polydipsia with reduction of vasopressin resistant urinary concentration capacity. Most cases showed anemia and pondostatural delay even at periods previous to renal insufficiency initiation. All cases showed normal urinary sediment with persistently negative urine cultures and progressed to chronic renal insufficiency after 1 to 10 years of evolution. Eight cases showed familial character. Histopathologic findings were similar and consisted of tubular disorders with alternation of atrophic tubuli having thickened basal and dilated tubuli having normal or flattened epithelium; renal medullary cysts were shown in some cases.