Previous studies of gender differences in the phenomenology of depression have focused mostly on symptoms as measured by self-report questionnaires or clinician-rated scales. In this study, we examined gender differences in the interpersonal behavior of depressed patients by using ethological techniques which involve direct observation of behavior. The nonverbal behavior of 72 nondepressed volunteers and 68 patients with a DSM-III-R diagnosis of nonpsychotic unipolar depression was videorecorded during clinical interviews and scored according to an ethological scoring system including 37 behavior patterns, mostly facial expressions and hand movements. Both male and female depressed patients showed a global restriction of nonverbal expressiveness reflecting a tendency towards social withdrawal. Nonverbal expression of hostility was the only behavioral category on which depressed patients scored higher than nondepressed volunteers. Even though clinical status exerted marked effects on the ethological profile, depression did not obscure some important differences in the nonverbal behavior of males and females. As a group, depressed women showed more socially interactive behaviors than depressed men. Their modality of interacting included higher levels both of nonverbal hostility and of submissive and affiliative behaviors. These results are discussed in view of clinical data indicating a relationship between gender, style of social interaction and response to antidepressant drugs.