Two nationally representative epidemiological samples (the National Longitudinal Alcohol Epidemiological Survey and the National Epidemiological Survey of Alcohol and Related Conditions) have been used to track changes in the prevalence of alcohol use disorders (AUDs) between 1992 and 2002 in the United States. Strikingly, estimates from these two data sets suggest that the lifetime prevalence of AUD increased by approximately 67% (from 18.2% to 30.3%) during this time frame. This article explores potential reasons for these discrepant estimates. Analyses indicated that a vast majority of change in lifetime AUD occurred with respect to alcohol abuse and not alcohol dependence. Most of this increase in abuse was attributable to self-reported changes in hazardous use that did not track with other archival measures of outcomes related to hazardous use in the population. Key methodological differences regarding the frequency requirements for prior-to-past-year alcohol abuse appeared to explain most of the discrepancy in lifetime AUD estimates. These findings, in conjunction with the relative lack of differences in the 12-month prevalence of AUDs, suggest that the discrepant lifetime estimates are likely due to methodological differences between the two surveys. These findings have important implications for substance use and other psychiatric surveillance and epidemiology where meaningful cross-temporal comparisons are desired.