One hundred subjects smoking more than 20 cigarettes per day were divided into two groups allocated at random to either nicotine gum or a placebo gum. Forty-eight subjects stopped smoking, irrespective of the treatment received. The magnitude of weight gain after given up smoking and the benefits of nicotine gum were evaluated. Weight gain was found to increase in ex-smokers compared with persistent smokers, but the increase was less pronounced in subjects who chewed nicotine than in those who chewed the placebo, although the difference was not statistically significant. However, enough gum must be chewed for the appetite and feeling of hunger to be reduced.