Emesis induced by inhibitors of type IV cyclic nucleotide phosphodiesterase (PDE IV) has been investigated in the ferret. The PDE IV inhibitors studied were: RS14203, R-rolipram and CT-2450 (i.e. (R)-N-{4-[1-(3-cyclopentyloxy-4-methoxyphenyl)-2-(4-pyridyl)ethyl]phenyl}N′-ethylurea), in addition to the less active enantiomers S-rolipram and CT-3405. Following oral administrations, different emetic profiles were observed with time. Emesis induced by RS14203 exhibited a dose–response relationship but no such relationship was seen for R-rolipram or CT-2450. The incidence of emesis was positively influenced by the dose of PDE IV inhibitors administered, allowing a rank order of potency: RS14203>R-rolipram>S-rolipram>CT-2450>CT-3405. PDE IV inhibitor-induced emesis was abolished by the tachykinin NK₁ receptor antagonist, CP-99,994. No peripheral release of substance P by PDE IV inhibitors seems to be involved in triggering the emetic reflex since L-743,310, which only has peripheral NK₁ receptor antagonist activity, was without effect. The implication of 5-HT₃ receptors in PDE IV inhibitor-induced emesis was variable. Our results suggest that the PDE IV inhibitors studied are mixed peripheral–central emetogens. PDE IV inhibition itself could be plausible mechanism of action of these agents. However, whether emesis is mediated via a specific isoform of PDE IV remains to be established.