The present study was conducted to provide baseline data for an anti-smoking educational program. Nineteen public senior high schools in a prefecture in Kyushu, Japan, participated in the study. In July 1982, unsigned self-administered questionnaires on smoking habits were answered by 4689 students--3088 males and 1601 females--during a homeroom under the supervision of their class teacher. The proportions of students who admitted that they had smoked cigarettes were 45.9% for males and 18.2% for females at the ordinary schools, and 78.1% for males at vocational schools. Eleven to twenty percent of male students had already smoked cigarettes in primary school. More male students in vocational schools had smoked than either male or female students in ordinary schools. Over 40% of vocational school students were regular smokers, in contrast to 11.8% for males and 3.4% for females at ordinary schools. It was also noted that the younger the students, the earlier the age at which they had smoked their first cigarette. The incidence of smoking at the primary school age appeared to be correlated with the incidence of smoking by a family member and at high school age with the incidence of smoking by a friend. Spending money and a friend who smoked were strongly associated with current smoking status of high school students, while parental smoking had a weak association. These results suggest the need for anti-smoking education beginning in a lower grade in primary school.