The effect of arginine vasopressin (AVP) on neurones in the dorsal cochlear nucleus (DCN) of young guinea-pigs of either sex was investigated in brainstem slices. Most impaled neurones fired in a regular manner, either spontaneously or following a depolarizing current injection. AVP, at concentrations of 10-1000 nM, excited 19/19 neurones from male and 16/19 neurones from female animals. This effect of AVP was concentration-dependent and could be mimicked by the V1 agonist [Phe2,Orn8]VT. Oxytocin was less potent than AVP and a selective V2 agonist, deamino-DAVP, was without effect. Thus, a class of DCN neurones is probably endowed with functional V1 vasopressin receptors. By making use of an antibody raised against the vasopressin-related glycopeptide, dense AVP-like immunoreactivity was found in the DCN of young animals of either sex.