Aims. To compare the occurrence of behaviours occurring under the influence of alcohol in 16-17-year-olds and determine associated risk factors for the different behaviours. Design/setting. Cross-sectional survey administered by laptop computers in secondary schools across the state of Victoria, Australia. Measurement/findings. The participation rate was 79%. Seventy per cent of participants drank alcohol; 17% of drinkers reported alcohol-related violence (accidents or injuries) and 15% reported problems relating to sex under the influence of alcohol (having sex and later regretting it or having had unsafe sex) in the previous 12 months. Males were more likely to report alcohol-related violence (20% compared to 14% females). Almost one in 10 young people reported having sex while under the influence of alcohol and later regretting it and 10% reported having had unsafe sex. There were no significant gender differences in the reporting rates of alcohol-related sexual risk taking (prop. cum. OR 1.1, 95% CI 0.68-1.9). For alcohol-related injuries, strong independent associations were found with dose of alcohol consumed (prop. cum. OR 2.3, 95% CI 1.3-4.0), frequency of alcohol consumption (prop. cum. OR 2.7, 95% CI 0.94-7.5), antisocial behaviour (prop. cum. OR 2.4, 95% CI 1.4-4.1) and peer drinking (prop. cum. OR 3.3, 95% CI 1.4-8.1). For alcohol-related sexual risk-taking, psychiatric morbidity (prop. cum. OR 4.1, 95% CI 1.9-9.0) and high frequency of alcohol consumption (prop. cum. OR 2.0, 95% CI 0.87-4.6) had strong independent associations. Conclusions. Physical injury and high-risk sexual behaviour under the influence of alcohol are common in teenagers. Alcohol-related physical injury appears closely related to patterns of alcohol consumption whereas alcohol-related sexual risk-taking is most closely associated with symptoms of depression and anxiety.