The minimum legal drinking age 21 (MLDA 21) legislation in the United States (U.S.) has been documented as one of the most effective public health measures adopted in recent times. This study reports on an effort to evaluate and interrelate a basic set of 16 laws directed at younger than age 21 youth that are designed to (a) control the sales of alcohol to youth, (b) prevent possession and consumption of alcohol by youth, and (c) prevent alcohol impaired driving by those younger than age 21. The first objective of this study was to determine whether there was any relationship between the existence and strength of the various underage drinking laws in a State and the percentage of younger than age 21 drivers involved in fatal crashes who were drinking. After controlling for various factors, the only significant finding that emerged was for the existence and strength of the law making it illegal for an underage person to use fake identification (p<0.016). The second objective was to determine if the enactment of two of the sixteen provisions (possession and purchase laws) was associated with a reduction in the rate of underage drinking driver involvements in fatal crashes. Analysis of variance (ANOVA) showed that there was a national 11.2% reduction (p<0.05) in the ratio of underage drinking drivers to underage non-drinking drivers in fatal crashes after the possession and purchase laws were adopted in 36 States and the District of Columbia (DC). This suggests that the two mandatory elements of the Federal MLDA 21 law are having the desired effect of reducing underage alcoholrelated highway deaths.