The study investigates the relationship between smoking and drinking, and the use of illicit drugs in a cohort of London adolescents. A high prevalence of drug experimentation and positive attitudes to illicit drug use were characteristic of those who both drank alcohol and smoked cigarettes on a regular basis. There was then a clear hierarchy in which lower prevalence of use and more negative attitudes marked those who only smoked, then those who only drank, while non-smokers and non-drinkers (the largest group) had lowest lifetime and recent drug use prevalence and the most negative attitudes about drug use.