The effect of 2-mg nicotine chewing gum as an adjunct to group therapy for smoking cessation was studied in a placebo-controlled, double-blind, randomized trial. After one year, 29% of the 106 subjects treated with nicotine chewing gum had remained abstinent throughout the year compared with 16% of the 99 subjects treated with placebo. The results were confirmed by measurement of levels of expired CO. More subjects in the nicotine group (70/94 v 45/93) reported that the gum reduced the craving for smoking. The adverse effects were few and not serious. In the nicotine group, 3% were still using the nicotine gum after two years. No subjects in the placebo group used the chewing gum beyond six months. Nicotine chewing gum is effective in improving the success rates in smoking cessation based on group therapy.