A case report of type II hyperprolinemia in a 5-year-old boy and its biochemical investigation is presented. The child has mild developmental delay, recurrent seizures of the grand mal type and EEG alterations. Although this disorder has been recently considered a benign condition, variants accompanied by characteristic symptomatology cannot be fully ruled out. The urinary excretion of high concentrations of N-(pyrrole-2-carboxylic acid)-glycine conjugate is stressed, since it appears that only one previous report in the literature described this compound in the urine of two patients affected by this disturbance.