The effect of disulfiram or nitrefazole pretreatment on ethanol induced hypotension was examined in urethane anesthetized rats. A relatively low dose of ethanol (150 mg/kg; i.p.) produced a characteristic hypotensive response in rats pretreated for various periods with disulfiram or nitrefazole. This hypotensive episode started 5-10 minutes following ethanol administration and lasted 40-60 minutes. The hypotensive response was not seen unless disulfiram or nitrefazole treatment preceded ethanol administration by a least 6-8 hours. The low dose of ethanol produced a plasma ethanol concentration of 10mg/100ml or less. One treatment with nitrefazole (200 mg/kg) rendered rats vulnerable to ethanol-induced hypotension for 6 but not 8 days. One treatment with disulfiram (200 mg/kg) lasted 4 but not 6 days. In addition, the hypotensive response was greater in rats treated with nitrefazole than in rats treated with an equal dose (200 mg/kg) of disulfiram.