We summarise a series of studies using a MAOI to help establish the validity of a subgroup of depressives referred to as atypical depressives. Patients with reactive mood meeting DSM-III criteria for depressive illness who had associated atypical features (which include hyperphagia, hypersomnolence, leaden paralysis, and rejection sensitivity) were randomised to imipramine, phenelzine and placebo. Non-responders were crossed over, and in all there were over 400 patient trials. Phenelzine consistently was found to be superior to imipramine. Only in trials which included patients lacking atypical, vegetative symptoms was imipramine found to equal phenelzine. We conclude that the researcher and the clinician should consider the relevance of the atypical depressive syndrome.