BACKGROUND Nicotine replacement therapies have proved to be of value in smoking cessation. However, not all smokers can use the nicotine gum or nicotine patch owing to side effects. In addition, the absorption of nicotine from these formulas is slow compared with smoking. A nicotine nasal spray delivers nicotine more rapidly. The objective of this study was to evaluate the efficacy and safety of the nicotine nasal spray for smoking cessation. METHODS Subjects were recruited through advertisements in newspapers and among patients referred to the smoking cessation clinic at Sahlgren's Hospital, Göteborg, Sweden. Two hundred forty-eight smokers were treated in small groups with eight counseling sessions over 6 weeks. At their first group session, subjects were randomized to a group receiving nicotine spray (n = 125), 0.5 mg of nicotine per single spray, or to a placebo group (n = 123). The procedure was double blind. Success rates were measured up to 12 months. The nonsmoking status was verified by expired carbon monoxide less than 10 ppm. RESULTS Significantly more subjects in the nicotine group were continuously abstinent for 12 months than in the placebo group (27% vs 15%; odds ratio, 2.16; 95% confidence interval, 1.15 to 4.12). Ten of the 34 abstinent subjects in the nicotine group used the spray for 1 year. Mild or moderate side effects were rather frequent for both sprays, but they were significantly more for the nicotine spray. Subjects with high scores (> 7) on Fagerström's tolerance questionnaire had a significantly lower success rate with placebo than with the nicotine spray. For subjects with low scores, there was no difference. CONCLUSIONS Nicotine nasal spray in combination with group treatment is an effective aid to smoking cessation.