This article explores the smoking behavior of 307 sixteen- to twenty-year-old students, and examines the relationships between their smoking and such factors as weight, exercise or morning diets. Four-year follow-up data on their physical characteristics, exercise and morning diet, and a five-year retrospective questionnaire on smoking habits were analyzed. Our longitudinal analysis revealed that: the prevalence of smoking increased from 17.6% to 54.1%, while the semi-annual incidence of smoking decreased from 12.0% to 4.3%. The number of cigarettes smoked per day increased for 3 years after the initiation of smoking, from less than 10 cigarettes per day in the first year to more than 15 in the third year. Although there was no relationship between smoking and exercise habits, smoking habits related significantly to morning diet. In the eighteen- and nineteen-year-old age category, smoking habits affected the weight of the subjects.