Smoking habits and body weight were registered on two occasions 3 yr apart in the county of Finnmark in 12,329 persons aged 20-49 yr. Among quitters, there was a mean weight increase of 2.7 kg for females and 3.6 kg for males; while among starters, there was a mean weight decrease of 0.9 for females and 2.5 for males. Mean weight continued to increase for at least up to 1 yr after quitting. A dose-response relationship was established between number of cigarettes smoked prior to quitting and weight gain. Females starting to smoke cigarettes reduced weight in proportion to daily cigarette consumption. There were no changes of clinical significance in main cardiovascular diseases risk factors with changes in cigarette consumption (and weight).