A prevalence study on smoking habits was carried out in 1991, among 864 school children from eight municipal schools in Sapiranga, in the State of Rio Grande do Sul, Brazil, from the 6th through 8th grade of primary school. Data was collected in class, using a questionnaire applied by trained teachers. Among students, 3.2% were smokers, although 20.3% had been exposed to tobacco. Males had begun the smoking habit at a mean age of 14.7 years and females at about 15 years old. The prevalence showed an increasing trend by age and individual school grade. As for gender, male smokers outnumbered females (p < 0,05). Smoking by older brothers and fathers seems to be positively associated with acquisition of the habit by school children.