In the ferret, 5-HT3 receptor antagonists are effective in controlling emesis produced by cytotoxic agents or radiation. To investigate the possibility that substance P has a role, as well as 5-HT, in the emetic reflex pathway, we have examined the anti-emetic effects of a NK1 receptor antagonist (racemic CP-99,994) in the ferret. Racemic CP-99,994 was effective against a range of emetogens, comprising cytotoxic drugs, radiation, morphine, ipecacuanha and copper sulphate.