A review was made of the clinical histories of 18 children who were admitted to the Emergency Department of the Hospital de Pediatría del C.M.N. (IMSS) with the diagnosis of nalidixic acid intoxication. The study covered a period of 3 years, from 1976 through 1978. There were no differences as to sex; infants under one year were most frequently attached; iatrogenesis was the most frequent mechanism. The clinical manifestations were characterized by neurological disorders of the state of alertness, hypertensive cranial syndrome and neuronal damage; there was metabolic acidosis in other cases. Treatment included gastric lavage, general measures, correction of acid-base unbalance, control of convulsive crises. Indications for the use of nalidixic acid are reviewed stressing that it must be used in urinary infections and as second choice drug.