The ability of arginine8 vasopressin (AVP) to potentiate the beta-endorphin-releasing activity of synthetic ovine corticotropin releasing factor (oCRF) was examined using an anterior-pituitary quarter assay. Both AVP and oCRF stimulated the release of beta-endorphin immunoreactivity (beta-END-I) in a dose-dependent manner, with AVP being approximately 10 times less effective than oCRF. Marked potentiation of beta-END-I release was observed when pituitary quarters were incubated in the presence of a combination of 0.5 nM oCRF and 1.0 nM AVP. Further potentiation was not observed when the higher doses of 1.0 nM oCRF and 2.0 nM AVP were tested in combination; however, maximal beta-END-I release may have been attained by the addition of 1.0 nM oCRF alone. These results suggest that AVP may play a role in the mediation of beta-endorphin release from the adenohypophysis.