To test the hypothesis that any change in urinary noradrenergic excretion accompanies drug-induced improvement in attention deficit disorder with hyperactivity, the authors gave pemoline (mean dose, 2.9 mg/kg of body weight) to 11 boys with this disorder in a 4-week open trial. Pemoline administration improved behavior but did not significantly change urinary catecholamine excretion. Serotonin excretion was unchanged, but phenylethylamine (PEA) and 5-hydroxyindoleacetic acid (5-HIAA) were significantly decreased. Clinical responders and nonresponders did not differ with respect to baseline urinary monoamine excretion or change in PEA and 5-HIAA excretion.