PURPOSE: To determine, by measuring the intracranial-parenchymal ratio at MR imaging, whether alcohol induces brain damage in social drinkers. MATERIALS AND METHODS: One hundred and five male adults aged 20 or over were selected for this study. They inclued 41 non-drinkers, 43 mild to moderate social drinkers, nine heavy social drinkers and 12 alcoholics. Using a workstation, the intracranial-parenchymal ratio was measured at four levels of T1-weighted MR images: the fourth, third and lateral ventricle, and the level of the centrum semiovale. The mean ratios of all four levels (I-IV) were also calculated Parenchymal ratios were compared between the four groups, and correlation between the amount of alcohol ingestion and the parenchymal ratio was also determined. RESULTS: The parenchymal ratio at levels I-IV was 80.31+/-3.73% in non-drinkers, 79.38+/-4.39% in mild to moderate social drinkers, 80.92+/-3.64% in heavy social drinkers and 73.48+/-4.42 % in alcoholics. The difference between alcoholics and the other three groups was statistically significant, but between non-drinkers and social drinkers was insignificant (ANOVA). Multiple regression analysis with control of the age factor revealed a decreased parenchymal ratio in mild to moderate and heavy social drinkers compared with non-drinkers, but without statistical significance. There was significant negative correlation between parenchymal ratio and amount of alcohol ingestion (Pearson correlation). CONCLUSION: There was significant brain atrophy in alcoholics, but no significant difference between nondrinkers and social drinkers. We thus conclude that social drinking does not induce significant alcohol-related brain atrophy.