We describe assays for homovanillic acid, hydroxymethylmandelic acid and dopamine that have proven practical and reliable during 3 years of routine use. Homovanillic and hydroxymethylmandelic acids were measured as trimethyl silyl derivatives by capillary gas chromatography. Dilution of samples prior to extraction was found to be necessary to achieve consistent recoveries of these acidic metabolites. Dopamine was assayed by high pressure liquid chromatography with electrochemical detection using an optimized method of catecholamine isolation that involved both ion exchange and alumina extraction. Untimed urine samples were collected from 140 hospitalized children. Age related reference data for the excretion of all three metabolites are reported. We suggest certain precautions that should be observed when using untimed samples and relating the results to creatinine excretion.