THIS STUDY is one in a series of continuing investigations Winsberg et aL, 1974b) which seeks to determine the relative effectiveness of various psychotropic drugs in controlling hyperactive/aggressive behaviors among children.In our previous work, we found the psychostimulants (dextroamphetamine and methylphenidate) to be comparable in effectiveness for the treatment of such behavior disorders (Winsberg et al., 1974b), while the tricyclic compound, imipramine, was also found to be effective in a study which compared it to dextroamphetamine . The findings from this research were consistent with our clinical experience in showing that many children fail to respond to each of these medications. Since pharmacotherapy with dextroamphetamine, mctliylphenidatc, and imipramine is frequently ineffective, and sinee the neuroIcptics (e.g. phenothiazines and butyrophcnones) are associated with dyskincsias (McAndrew et al., 1972; PoHzos et aL, 1973) and other potentially noxious side effects (Winsberg et al., 1976), alternative drugs are clearly needed.In our ongoing clinical work, another tricyclic, amitriptyline, has been useful for some of these children. There is also research evidence which points to the potential utility of this compound in treating children with behavior disorders. Kraft et al. (1966) in a noncontroUed study, found amitriptyline to be effective in 60% of outpatient children with different psychiatric problems. Krakowski (1965) studied 50 hyperkinetic children whose diagnoses included: neurosis, psychophysiological disorders, mental deficiency, schizophrenia, neurotic traits, and habit and conduct disorders. Sixty per cent ofthe children with the diagnosis of conduct disorders were reported to have a good or excellent response to amitriptyline therapy. However, a major weakness of that study was that the prime behavioral dependent measure was a subjective clinical evaluation. Lucas et al. (1965), in a double-blind study, used amitriptyline for childhood depressions and found that the behavior category in w hich the greatest number of patients improved was that which the authors termed "problems of external control." The latter report does not allow for a more precise categorization of the subjects' behavior problems.