In a cohort study of 1080 pupils who were followed for 5 years from when they left compulsory school (from age 16 to age 21 years), smoking habits were found to correlate with unemployment among both boys and girls. Pupils who were smokers in school had a higher risk of becoming unemployed than non-smokers. Irrespective of early smoking, smoking habits developed more unfavourably among unemployed young people than among those with no unemployment during the period studied. The odds ratio of being a smoker at the age of 21 years when unemployed more than 20 weeks during the observation period, compared with those without or with short unemployment, was 2.44 for men and 3.45 for women. When adjusted for the influence of socio-economic background, education, economy and smoking habits at the start of the period, the odds ratio was 1.7 (95% CI 1.01-2.86) for men and 2.0 (1.13-3.53) for women. The adjusted odds ratio for increasing or starting smoking during the period was 1.5 (95% CI 0.89-2.56) for men and 2.0 (1.18-3.35) for women. No significant correlation was found between snuffing and unemployment. Thus, it seems that unemployment is a risk factor for development of tobacco smoking in young people, especially among women.