A prospective cohort of 74,332 men and women was used to investigate the association of body mass index and height with suicide, anxiety, and depression. Participants in the Nord-Trøndelag Health Study (Norway, 1984-1986) (HUNT 1) were aged 20 years or more and followed up until December 31, 2002. Anxiety and depression were measured with the Hospital Anxiety and Depression Rating Scale (HADS) in 1995-1997. There were 183 suicides. Suicide risk decreased with increasing body mass index at baseline (1984-1986) in men and women. In models controlling for a range of psychological, social, and lifestyle factors, the hazard ratio per standard deviation increase in body mass index was 0.82 (95% confidence interval: 0.68, 0.98). In contrast, in the subset of participants (n = 44,396) with HADS measures, body mass index at baseline (1984-1986) was positively associated with depression. In fully adjusted models, the odds ratio for depression per standard deviation increase in body mass index (HADS-D: > or =8) was 1.11 (95% confidence interval: 1.07, 1.15). In fully adjusted models, there was no association of height with the incidence of suicide or depression. Raised body mass index is associated with an increased risk of depression but reduced risk of suicide in men and women. The mechanisms underlying these different associations require clarification.