The concepts of psychosocial and psychomotor inhibition characteristic of major depression are based primarily on clinical observations. It is possible to describe and define these two types of inhibition by means of a systematic, quantitative ethological (behavioral) approach, which singles out precise and significant behavior markers. This investigation focuses on the behavioral features of psychosocial and psychomotor inhibition in 11 hospitalized depressed subjects and their changes during clinical recovery. The hypothesis that major depression is characterized by a significant reduction of social interaction is tested (psycho-intellectual inhibition is not addressed). Results show significant behavioral differences between depressed and recovered subjects with depression being characterized by a significant reduction of social interaction, whereas self occupation and body mobility are reduced to a lesser degree. Behavior markers for depression include nonspecific gaze, withdrawal, no mouth movements, no eye region movements, and social inactivity. Behavior markers for recovery include socially interested, social smile, verbal social initiative, speech, nod, raised eyebrows, wrinkled eyebrows, social laughter, gesticulation, drum one's fingers, point, and help. Findings point to tendencies toward two types of major depression and two types of recovery. A companion paper (Schelde, this journal) addresses theoretical issues.