The prevalence of cigarette smoking in Australian secondary school students in 1993 was estimated from a survey of 22 696 12- to 17-year-old students from 332 secondary schools (and feeder schools) in all states and the Northern Territory. Self-administered questionnaires were answered anonymously by groups of up to 20 students selected randomly from school rolls, a method that replicated previous surveys in 1984, 1987 and 1990. Current smoking (smoking at least one cigarette in the week preceding the survey) at 12 years of age was 8 per cent in boys and 7 per cent in girls, but in those 17 years of age the prevalence was much higher (28 per cent of boys, 31 per cent of girls). Age was also associated with the mean number of cigarettes smoked per week by current smokers (8.6 in boys and 7.0 in girls at age 12 and 43.8 in boys and 32.0 in girls at age 17). After controlling for sex, age, school type and state of residence, the percentage of 12- to 15-year-olds who were current smokers rose from 15.7 per cent to 17.5 per cent between 1990 and 1993, an effect that was more pronounced in boys. On the other hand, the mean number of cigarettes smoked by 12- to 15-year-old current smokers dropped from 23 per week to 19.5, and the reduced consumption was greatest in boys. Furthermore, there was no increase in the proportion of students who smoked on three or more days per week, which suggests the increase was limited to occasional, casual or social smoking.