This paper reports on an ethological study of 11 depressed hospitalized subjects. Major depression and recovery are described in terms of general behavioral traits, i.e., behavior parameters. The hypothesis, that the primary behavioral feature of major depression is a reduction of social interaction and that secondary features are reduced self occupation and body mobility (posture flexibility) is tested. The behavioral patterns of depression and recovery are described and elucidated by 12 defined behavioral parameters, eight of which show significant changes between the first and the last hospital week. Findings from six of the parameters are consistent with the hypothesis and demonstrate social inhibition during depression; interactions between depression and nonverbal behavior are particularly striking. Findings also confirm that, during depression, self occupation and body mobility are reduced to a less significant degree than social inhibition. Possible relationships between findings and agitated forms of major depression are discussed. A final section examines findings in an evolutionary context and emphasizes their clinical implications.