The reduced speech activity of depressed patients is a consistent finding in many systematic studies. However, this and other nonverbal parameters have seldom been investigated in psychopharmacological studies. In this double-blind study, 21 retarded depressed patients were treated with amitriptyline or pirlindol over a four-week period. The speech behavior of the patients was analyzed by computer techniques, and the drug-induced changes in these variables were compared with the psychopathological effects of the treatment.