Actometry is a technique that enables continuous monitoring of spontaneous motor activity. This technique can be applied to the study of depression either by studying qualitative motor activity patterns or by measuring quantitative motor parameters. We present here the results of a quantitative actometric analysis. 13 depressive in-patients were evaluated both clinically by depression scales and by actometry before and after trimipramine treatment. Correlation analysis was made between actometric and clinical rating scores at different moments of the treatment. Some actometric parameters appear to be specific indices of depression and psychomotor retardation. Future prospects for the use of actometric techniques in depression are discussed.