The Young-HUNT Study is the adolescent part (13-19 years) of HUNT, the Nord-Trøndelag Health Study, Norway. Three cross-sectional surveys have been conducted: Young-HUNT1 (1995-97), Young-HUNT2 (2000-01) and Young-HUNT3 (2006-08). Major public health issues, including somatic and mental health, quality of life and health behaviours are covered. Young-HUNT was performed in schools visited by trained nurses. Data collection included self-reported questionnaires, structured interviews, clinical measurements and, in Young-HUNT3, buccal smears. The total response rates varied from 90% to 83% and the Young-HUNT database includes 17 820 teenagers. Some Young-HUNT1 participants constitute the baseline for two follow-up studies: a 4-year follow-up through adolescence to Young-HUNT2 and an 11-year follow-up into young adulthood to the adult HUNT3. Longitudinal data are also obtained by linkage of data from Young-HUNT to different national health registers. Linkage to family registers allows the possibility of studying genetic and environmental interactions through generations. Presently 20 PhD students are working with the data, 11 Young-HUNT based PhD theses have been completed and more than 50 scientific papers published.