Association between aggression and heavy alcohol use is documented in the literature in various disparate samples and settings. Comparison of trait aggression levels using a uniform methodology across different samples is almost entirely lacking. This study compared trait aggression levels of treated inpatients with severe alcohol-related problems with those of a nationally representative sample of the general adult population using the same methodology. Results indicated that in the patient population the trait aggression levels were substantially higher than in the general population. Because several studies have demonstrated that aggressive personality traits are closely linked with violence after drinking alcohol, our results further highlight the importance of treatment programs in this at-risk population. From a methodological perspective, the higher trait aggression level of inpatients with alcohol-related problems compared with the general population supports the assumption that the underrepresentation of alcoholics in the population surveys may restrict the range in the severity of alcohol use and dependence, and may therefore produce severely biased results in such studies.