The activity of tianeptine (2.5 and 5.0 mg/kg twice daily, i.p.) and of sertraline (5.0 mg/kg, twice daily, i.p.) were assessed in three animal models of depression. In the Behavioural Despair Test, acute treatment with sertraline or tianeptine (5.0 mg/kg) significantly reduced the immobility time. In the olfactory bulbectomized (OB) rat model, chronic treatment with tianeptine (2.5 and 5.0 mg/kg) or sertraline (5.0 mg/kg) antagonized the lesion-induced hyperactivity in the ''open field'' apparatus. The hypothermic response to the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT, 0.15 mg/kg, s.c.) was significantly attenuated after chronic setraline treatment, whereas tianeptine was inactive at the 2 doses tested. Neither drug affected the hypersection of corticosterone that occurs at the light:dark interface. A reduction in the serotonin metabolite 5-HIAA was found in the hypothalamus of sertraline-treated sham rats. It can be concluded that although the neurochemical properties of sertraline and tianeptine differ, they demonstrate similar antidepressant-like activities in the Behavioural Despair and OB rat models. The lack of effect of tianeptine on the 8-OH-DPAT-induced hypothermic effect indicates that it does not induce 5-HT1A subsensitivity, contrary to most antidepressants.