In July 1984, a Federal law was enacted establishing a national minimum drinking age of 21 years. Public Law 98-363 required that a portion of Federal aid highway funds be withheld from those States that had not, by law, established 21 years as the minimum drinking age by September 30, 1986. Critics have attacked the law as controversial because it restricts a specific age group's access to alcoholic beverages. They have also questioned the effects the law has on highway safety. After analyzing the 49 evaluations of laws raising the legal drinking age, the study concludes that raising the drinking age has a direct effect on reducing alcohol-related traffic accidents among youths affected by the laws. A higher legal drinking age also reduces the number of traffic accidents in a State. Raising the legal drinking age also results in less alcohol consumption and less driving after drinking by the age group affected by the law. There is only limited evidence for assessing if a higher drinking age protects youth younger than the minimum age from traffic accidents. Insufficient evidence exists to assess the extent to which under-aged youths cross State lines to obtain alcoholic beverages. Long-term effects of the new law cannot yet be measured. Study materials are appended. 83 references.