Objectives. The study examines stages of drinking and smoking careers and transitions from initiation to regular use among adolescents, as a function of ethnic status and gender. Design. The data were collected using a confidential, self-completion questionnaire assessing onset and frequency of drinking and smoking. The sample consisted of 1777 adolescents, between the ages of 11 and 14, drawn from eight secondary schools in south-west London. Results. For both smoking and drinking, white children were more likely to have ever smoked tobacco and drunk alcohol, and were also more likely to progress from initiation to regular use than were either black or Asian children. Asian children reported the latest onset and the lowest prevalence rates for both drinking and smoking. Males reported experimenting with both cigarettes and alcohol at an earlier age than females, although a lower proportion of males report regular and lifetime involvement with both alcohol and tobacco. Furthermore, a significantly higher proportion of females who try smoking go on to do so regularly. Discussion. The importance of sociocultural factors in relation to race and gender in predicting onset and escalation of substance use is discussed. The fact that age of onset floes not appear to be a significant determinant of transition rate from initiation to regular use is also explored.