To understand the pathophysiology of Attention Deficit Disorder with Hyperactivity (ADDH), and to develop new treatments, a therapeutic trial of the amino acid, d-phenylalanine, was completed over the past nine months. Eleven ADDH boys participated in a placebo controlled double-blind evaluation of phenylalanine (20/mg/kg/day) and placebo. Phenylalanine had no significant effect upon behavior in spite of elevated blood phenylalanine levels (up to 120 un/l). In an attempt to localize abnormal patterns of cerebral glucose metabolism and cerebral flow in adults with Attention Deficit Disorder (ADD) Residual Type, parents of diagnosed hyperactive children are being studied using the 2-deoxyfluoroglucose method of Positron Emission Tomography (PET). To date, 18 patients have been scanned; preliminary results showed decreased cortisol glucose utilization. Eleven parents were rescanned after receiving dextroamphetamine; results are being analyzed. Because of reports that the spinal fluid (CSF) 5HIAA, a serotonin metabolite; may be low in severely impulsive or aggressive adults, a study has been initiated to compare spinal fluid catecholamine and indoleamine metabolites in severely aggressive, conduct disordered children with and without ADD to children with other neurological problems. Peripheral measures of catecholamines will also be obtained.