Inactive aldehyde dehydrogenase-2 (ALDH2) is known as a genetic negative risk factor for the development of alcoholism. In alcoholics with inactive ALDH2, unidentified factors that overcome the adverse reactions of high blood acetaldehyde concentration after drinking may increase such persons' susceptibility to alcoholism. Comparison of clinical characteristics, including sociofamilial backgrounds and psychopathologies, failed to show significant differences between alcoholics with inactive ALDH2 (inactive group) and those with active ALDH2 (active group). Examination of the temporal profile of disease development showed that the inactive group experienced each stage or event in the history of drinking and alcoholism 1 to 5 years later in life than the active group; however, not all comparisons reached statistically significant levels. Although preliminary, these results suggest that an inactive ALDH2-mediated delay in the occurrence of alcohol-related problems seems to contribute to the suppression of alcoholism development.