The correlation among degrees of alcohol intoxication, facial flushing, blood alcohol concentration (BAC) and blood acetaldehyde level was studied in 117 male alcoholic patients who underwent various tests to assess alcohol influence. Blood samples were collected and alcohol and acetaldehyde levels were determined. BACs ranged from 29 to 577 mg/dl in all patients and from 200 to 299 mg/dl in 48 of them. Fifty-one patients could stand erect (mean BAC [+/- SD] = 189 +/- 80 mg/dl), while 48 showed apparently normal reaction to a walking and turning test (mean BAC = 192 +/- 78 mg/dl). Some of the cases having BACs over 300 mg/dl could still stand and walk while others with BACs under 100 mg/dl already showed psychomotor impairment. Facial flushing was recognized in 75% of the subjects. Acetaldehyde concentrations in 27 patients ranged from 24 to 147 micrograms/dl. Appearance of facial flushing was correlated with relatively high concentrations of blood acetaldehyde. Seven out of 10 healthy volunteers given 1.6 to 2.0 g/kg of alcohol as a control could do nothing but sleep after reaching peak BAC (mean = 232 +/- 21 mg/dl). These findings are taken to indicate a great difference in response to alcohol between alcoholics and healthy men. This study is the first to report the occurrence of facial flushing and raised blood acetaldehyde concentration among Japanese alcoholics.