Three methods were employed to assess whether human volunteers (Caucasian, Asian or Cree Indian) possessed the typical or atypical mitochondrial aldehyde dehydrogenase (ALDH2) isozyme. These methods were: (1) questionning individuals about facial flushing responses following alcohol consumption; (2) application of the ethanol skin patch test, and (3) direct analysis using isoelectric focusing and activity staining of ALDH activity in hair root samples. The results from the three methods were in good agreement and revealed that only the typical ALDH2 isozyme was expressed in Saskatchewan Cree Indians. In agreement with previous reports, the typical ALDH2 was expressed in the Caucasian group of subjects, while both the typical and atypical forms were expressed in the Asian subjects.