A questionnaire relating to smoking habits, respiratory symptoms, and health attitude was administered to schoolchildren aged between 11 and 17 throughout a defined geographical area in both 1975 and 1979, with a valid response from 10498 and 12002 young people respectively. Each cohort was almost entirely different. The results suggest that although the prevalence of regular smoking has decreased in boys from 16 to 13% it has increased in girls from 13 to 14% and that at all ages more girls smoke more than boys. However despite the fall in the prevalence of regular smoking in boys there has been an overall increase in cigarette consumption. Young people who are regular smokers predominantly smoke middle tar cigarettes while among experimental smokers there is a high incidence of low tar smoking, which might suggest that such cigarettes facilitate the taking up of the habit in children. The previously described relationships between smoking and respiratory symptoms was confirmed. During the 4-year study period young people's knowledge of the associated links between smoking and heart disease and stroke has increased appreciably. It is suggested that specific health education during the years 1975-79 has not been successful, and there is the need for research.