Three Rhesus monkeys were removed from their mothers at birth and reared together in a group cage. When they were one year old they were subjected to repeated separations during which they were placed alone for 1 hour in another cage in an acoustically isolated adjacent room. The number of vocalizations and gross body movements were recorded automatically. Single injections of imipramine (3.75, 7.5 and 15 mg/kg IM) instead of decreasing tended to increase the number of vocalizations without affecting motor activity. A similar pattern was observed when imipramine (3.75 and 7.5 mg/kg IM) was administered repeatedly (2 injections/day/4 days). The failure of imipramine to decrease separation-induced vocalizations in our conditions suggests that the procedure would not be useful for testing potential antidepressants.