In the tail suspension test (an animal model of depression) the duration of immobility during the 6 min of observation was 56.84 +/- 6.54 sec in sham-ovariectomized mice and 113.11 +/- 7.86 sec 30-32 days after ovariectomy. Estradiol (10, 100 or 1,000 micrograms/kg) and progesterone (50, 1,000 or 10,000 micrograms/kg), subcutaneously injected daily 4 times before the test, restored the duration of immobility in ovariectomized mice to normal, while having no effect on sham-operated animals. On the other hand, desipramine (20 mg/kg IP 1 hr before testing) significantly reduced the duration of immobility both in ovariectomized and in sham-operated mice. These data indicate that ovarian sex hormones, while having no "antidepressant," desipramine-like, effect on the behavior of intact adult female mice, have such an effect in ovariectomized mice, and enable the animal to cope in a "normal" way with adverse environmental situations.