OBJECTIVE: To investigate the change in food habits in Swedish adolescents between 15 and 21 y of age with reference to age, sex, region and socioeconomic background. DESIGN: A longitudinal study from 1993 to 1999. SETTING: Two different regions in Sweden, the university city of Uppsala and the industrial town of Trollhättan. SUBJECTS: On three different occasions, 1993, 1995 and 1999, 208 adolescents, 96 males and 112 females, were studied. METHODS: A food frequency questionnaire containing 29 different food groups was used. The questionnaire also contained questions about food habits and amounts of some food items and socioeconomic conditions of the participants and their families. RESULTS: At 17 and 21 y of age, the adolescents consumed significantly more often pasta, vegetables, coffee and tea compared to age 15, while the frequency consumption of fat spread, milk, bread, potatoes, carrots and buns and biscuits decreased. The changes between 15 and 17 were smaller than between age 17 and 21. At age 21, the males decreased their intake of fruit, while the females decreased their intake of meat. No-meat consumers among females increased from 2 to 13%. Higher educational level of the mothers of the adolescents was associated with more frequent consumption of vegetables and pasta between ages 17 and 21. Milk consumption decreased significantly in both sexes. Breakfast habits did not change: 90% had breakfast five times/week or more. CONCLUSIONS: Food habits change significantly during adolescence along with lifestyle changes. Therefore, health promotion during adolescence ought to be more supported by the society.