In this large-scale study, we examined the relationship between an adolescent's sexual behavior and drinking style. Three aspects of sexual risk-taking were included: early activity, unprotected sexual intercourse and having sex with multiple partners. A distinction was made between different drinking styles, i.e. alcohol drinking and drunkenness-related drinking. Cross-sectional school survey data from the School Health Promotion Study was collected in Finland in 2002–2003. The national sample consisted of adolescents from the eighth and ninth grades (n = 100 790). The mean ages were 14.8 and 15.8 years. Using logistic regression analysis, we investigated the association between sexual behavior and drinking style among teenagers. The likelihood of engaging in sexual intercourse increased with the frequency of alcohol use. In particular, frequent drunkenness-related drinking increased the probability that the teenager had experienced sexual intercourse. The likelihood of engaging in unprotected sex and/or having multiple sexual partners was many-fold for adolescents drinking frequently until they were in a state of drunkenness. Particularly for girls, weekly drunkenness-related drinking was associated with multiple partners. The vast majority of sexually experienced under-aged adolescents drink alcohol, many of them until they are drunk. Thus, it could be effective to combine both alcohol education and sex education, including contraceptive counseling, in early adolescence.