The dipsogenic responses of female rats to administration of angiotensin II (150 micrograms/kg b.w., IP), pilocarpine (3 mg/kg IP), hypertonic saline (1 M NaCl solution, 1% b.w.), and a 24 hour dehydration were attenuated by acute IP administration of graded doses of the central and peripheral alpha 2-adrenergic agonist, clonidine. For all treatments except dehydration, clonidine inhibited significantly the dipsogenic response at the lowest dose used (6 micrograms/kg, IP). The first significant effect on dehydration-induced drinking required approximately a 4 fold higher dose (25 micrograms/kg, IP). Attenuation of the response to these dipsogenic stimuli by clonidine, suggests that its ability to stimulate alpha-adrenergic receptors centrally may play an important role in its dipsogenic inhibitory activity.