The doses of propofol that produce loss of consciousness were investigated in 26 patients with chronic alcoholism and in 20 patients with a history of small alcoholic intake undergoing ear, nose, and throat surgery under general anesthesia. Last ethanol consumption by the alcoholics was 24 h preoperatively, as they had no access to alcohol when admitted to the hospital. Propofol was infused at a rate of 1200 mL/h (200 mg/min). The doses required to produce (a) loss of verbal contact and (b) loss of ability to grasp a 20-mL syringe filled with water were recorded. At this time a 2-mL venous blood sample was collected to detect propofol blood concentrations. A painful stimulus was applied to the abdomen, and a positive or negative response was noted. The mean +/- SD dose of propofol required for loss of verbal contact was 2.7 +/- 0.42 mg/kg in the alcoholic group and 2.2 +/- 0.43 mg/kg in the control group (P < 0.001). The dose of propofol required for dropping the syringe was significantly higher in the alcoholic group, 4.2 +/- 1.02 mg/kg versus 3.2 +/- 0.75 mg/kg in the control group (P < 0.01). The two groups did not differ significantly regarding the propofol blood concentrations at loss of consciousness, or the frequency of response or no response to painful stimulus. These findings suggest that the doses of propofol required to induce anesthesia in chronic alcoholic patients are more than in patients who drink socially.