The control of the formation of rabbit oviduct fluid and its relationship to the secretion of chloride ions has been studied using an in vitro vascularly perfused preparation. Fluid was produced at a rate of 43.41 microliters h-1 in oviducts from rabbits in oestrus. The rate was increased by isoprenaline and tetraethylammonium, decreased by dibutyryl cAMP, dihydro4,4'diisothiocyanatostilbene-2,2'-disulfonic acid (H2DIDS), and propranolol, while amiloride had no effect. H2DIDS induced a small decrease and isoprenaline a small increase in vascular to lumen Cl- flux but propranolol and dibutyryl cAMP had no effect. Oviducts from pseudopregnant animals treated with hCG three days before the experiment produced significantly less fluid than did those from rabbits in oestrus, but there was no difference in vascular to lumen Cl- flux. The concentration of K+ in oviduct fluid formed in vitro was more than three times higher than in the vascular perfusate. The ability of adrenergic agents to influence the formation of rabbit oviduct fluid could have clinical implications in the prevention or treatment of female infertility due to blockage of the Fallopian tubes and might also be useful in enhancing the secretory activity of oviduct cells maintained in co-culture with early embryos.