In preparation for a comprehensive intervention project concerned with smoking behavior, physical activity, nutrition, and alcohol, an exploratory study of 800 public school and gymnasium pupils in the seventh and ninth grades (12–16 years old) was undertaken. The median of total serum cholesterol dropped from 4.8 mmol/liter in 12-year-old pupils to 4.2 mmol/liter in 16-year-olds. The decrease was greater in boys than in girls (0.7 versus 0.4 mmol/liter). The systolic and diastolic blood pressures rose slightly with age in boys and girls. The prevalence of occasional and daily smokers was 19.8 and 21%, respectively. The proportion of daily smokers was 36.4% among public school students (lower socioeconomic status) versus 4.1% among gymnasium pupils (higher socioeconomic status). Similar differences were found for the serum thiocyanate levels.