The effect of hypotensive haemorrhage on blood pressure recovery was compared in saline- and streptozotocin-injected rats. Absolute plasma volumes (and calculated blood volumes) were not different between the two groups. After haemorrhage of similar volumes at similar rates, there were no significant differences in the recoveries in blood pressures or heart rates between control and diabetic animals. In other control and diabetic groups, posthaemorrhage treatment with the converting enzyme inhibitor captopril (at 20 min) and the vasopressin (V1-receptor) antagonist d(CH2)5DAVP (at 40 min) did not have any deleterious effects on blood pressure recovery at these times. These results support the proposition that neither the renin-angiotensin system nor vasopressin are importantly involved in blood pressure recovery at these time points after hypotensive haemorrhage in conscious rats. They are also consistent with the lack of difference between untreated control and diabetic groups, despite previous findings showing impairments of renin-angiotensin- and vasopressin-mediated effects after acute hypotension induced by pentolinium in diabetic rats.