AIM: This study examined the earliest stages in drug involvement, in terms of the relationship between alcohol and tobacco use, among adolescents from six European countries (Denmark, Finland, the Netherlands, Portugal, Spain and the United Kingdom). International, gender and age differences were studied. DESIGN, SETTING AND PARTICIPANTS: A large international sample of European adolescents (n = 10170, mean age = 13.3 years) was followed longitudinally. Data were gathered in the autumn terms of 1998 and 1999 by means of self-administered questionnaires. MEASURES: Adolescents' self-reports on smoking and alcohol behaviour were used. Both behaviours were classified into two categories, that of adolescents who had never used the substance and that of those who had used the substance at least once in their lives. Logistic regression was used to determine which substance was the best predictor of the subsequent use of the other substance. FINDINGS: Alcohol use and tobacco use were found to be associated with each other reciprocally. Results revealed that in Europe as a whole, tobacco use predicted subsequent alcohol use better than the converse. However, for Dutch girls, alcohol use predicted subsequent smoking behaviour better than the converse. CONCLUSION: The findings suggest that the development of alcohol and tobacco use patterns are closely related, but the order of progression is not universal and may reflect cultural factors.