Research has showed that children of alcohol abusers struggle with an array of psychological and behavioral problems. Although research has established an increased risk of adverse outcomes for this group, individual and gender based differences indicate a complex relationship. NOU 2003:4 and Opptrappingsplan for rusfeltet emphasize the need for knowledge about the harmful effect of parental alcohol abuse on the offspring. The present study aims at 1) investigating the impact of parental alcohol abuse on the offspring's mental health, and 2) identify factors that modify effects on offsprings mental health in families with alcohol abusing parents. Poor mental health is observed as symptoms of depression and anxiety, low self-esteem and subjective well-bein g. Measures of possible moderator variables, such as personality, family environment, leisure activities, and socio-demography and mental health of parents were also included. The mental health of children of alcohol abusers will be investigated longitudi nally and cross-sectionally. As previous studies have been largely cross-sectional, based on clinical samples and conducted in different cultures, the present study will provide insight into research areas in need of exploration. The study is based on the Nord-Trøndelag Health Study, consisting of adult data (HUNT I, II and III) and adolescent data (UngHUNT II, a follow up-survey and UngHUNT III). HUNT I was conducted in 1984-86, HUNT II in 1995-97, whereas HUNT III will be terminated in June 2008. UngHUN T II and III were conducted at the same time as HUNT II and III, and the follow up survey was conducted in 2000-01. The data from the HUNT studies were matched with data from public registries, enabling the matching of self-report and registry data from p arents and their offspring. The 3 % having the highest alcohol consumption were defined as cases. Approximately 500 children and 500 adult offspring are expected to have (had) alcohol abusing parents.