Underage drinking contributes to the 3 leading causes of death (unintentional injury, homicide, and suicide) among persons aged 12 to 20 years. Most adverse health effects from underage drinking stem from acute intoxication resulting from binge drinking. Although binge drinking, typically defined as consuming > or = 5 drinks on an occasion, is a common pattern of alcohol consumption among youth, few population-based studies have focused specifically on the characteristics of underage binge drinkers and their associated health risk behaviors. We analyzed data on current drinking, binge drinking, and other health risk behaviors from the 2003 National Youth Risk Behavior Survey. Prevalence estimates and 95% confidence intervals were calculated by using SAS and SUDAAN statistical software. Logistic regression was used to examine the associations between different patterns of alcohol consumption and health risk behaviors. Overall, 44.9% of high school students reported drinking alcohol during the past 30 days (28.8% binge drank and 16.1% drank alcohol but did not binge drink). Although girls reported more current drinking with no binge drinking, binge-drinking rates were similar among boys and girls. Binge-drinking rates increased with age and school grade. Students who binge drank were more likely than both nondrinkers and current drinkers who did not binge to report poor school performance and involvement in other health risk behaviors such as riding with a driver who had been drinking, being currently sexually active, smoking cigarettes or cigars, being a victim of dating violence, attempting suicide, and using illicit drugs. A strong dose-response relationship was found between the frequency of binge drinking and the prevalence of other health risk behaviors. Binge drinking is the most common pattern of alcohol consumption among high school youth who drink alcohol and is strongly associated with a wide range of other health risk behaviors. Effective intervention strategies (eg, enforcement of the minimum legal drinking age, screening and brief intervention, and increasing alcohol taxes) should be implemented to prevent underage alcohol consumption and adverse health and social consequences resulting from this behavior.