In the present study we examined the effect of different drugs on the m-trifluoromethylphenylpiperazine (TFMPP)- and m-chlorophenylpiperazine (m-CPP)-induced hypothermia in mice. Both the hypothermias studied are blocked or reversed by pindolol, cyanopindolol and compound 21-009, but not by atenolol. Neither hypothermia is antagonized by 5-HT1A antagonists (ipsapirone, spiperone), a 5-HT1C antagonist (mesulergine), 5-HT2 antagonists (cyproheptadine, mianserin, methysergide), 5-HT3 antagonists (ICS 205930, metoclopramide). The examined hypothermias are not antagonized by other antihypothermic agents (pimozide, idazoxan, atropine). The 8-OH-DPAT-induced hypothermia is not affected by cyanopindolol or compound 21009. The obtained results indicate that the TFMPP- and m-CPP-induced hypothermias in mice are mediated by 5-HT1B. These hypothermias may be a good screening test for evaluation of the 5-HT1B-agonistic and 5-HT1B-antagonistic activity.