In a prospective study, the authors compared 22 delusional and 36 non-delusional depressive patients with respect to demographic and clinical variables, personality, and response to treatment. Delusional depressives had a higher total score than non-delusional depressives on Hamilton's Rating Scale for Depression, as well as a higher score for depressed mood and psychomotor retardation. The type of treatment failed to differentiate the two groups as to outcome at discharge. However, six of the seven delusional depressives who did not respond to tricyclic antidepressants had a full recovery with ECT. The results indicate that delusional depression represents a more severe type of major depression.