Activation of subfornical organ (SFO) efferents has been reported to increase the excitability of paraventricular nucleus (PVN) neurons projecting to cardiovascular centres in the medulla. Such findings suggest a role for these neural projections in the cardiovascular effects of systemic angiotensin II (AII) acting at the SFO. The present studies examine the effects of peripheral AII (50-500 ng) on the activity of PVN neurons antidromically identified as projecting to the dorsomedial medulla (DM). A total of 68 neurons were tested, of which 25% were found to be specifically activated by AII, and 25% inhibited as a consequence the increased blood pressure accompanying administration of this peptide. The activity of the remaining neurons tested was unaffected by AII. These studies demonstrate that only a small proportion of PVN neurons projecting to the DM, which have been shown to be influenced by SFO efferents, are also activated by systemic AII. Such data do however, support a significant role for these neurons in the cardiovascular functions of SFO.