Several studies have reported on comorbidity between depression and anxiety. The present study investigates the occurrence of anxiety symptoms during an episode of unipolar depression. The authors administered the 15-item Rating Scale for Anxiety States of Hamilton (HAM-A) to 73 depressed inpatients categorized according to DSM-III criteria into minor (300.40,309.00), major depression without (296.X2) and with (296.X3) melancholia. Principal-component (PC) anylsis revealed three inter-pretable PCs: a somatic anxiety, a depression-anxiety overlap, and an anxious mood-behavior factor. Subjects with major depression showed significantly higher ratings on total HAM-A score, the three above PCs, and on all HAM-A items (except general somatic muscular and genitourinary symptoms) than subjects with minor depression. A cluster analysis generated two stable, qualitatively distinct clusters: i.e. one with severe anxiety and one with no or minimal anxiety; the six most discriminating symptoms were: tension, behavior at interview (general or physiological), respiratory, genitourinary and autonomic symptoms. Up to 95.4% of patients allocated to the severe anxiety cluster were major depressives. The results suggest that major depression may be divided into two qualitatively distinct classes, i.e. major depression with and without anxiety features.