Objective To evaluate the efficacy of using a nicotine patch for 5 months with a nicotine nasal spray for 1 year. Design Placebo controlled, double blind trial. Setting Reykjavik health centre. Subjects 237 smokers aged 22-66 years living in or around Reykjavik. Interventions Nicotine patch for 5 months with nicotine nasal spray for 1 year (n = 118) or nicotine patch with placebo spray (n = 119). Treatment with patches included 15 mg of nicotine for 3 months, 10 mg for the fourth month, and 5 mg for the fifth month, whereas nicotine in the nasal spray was available for up to I year. Both groups received supportive treatment. Main outcome measure Sustained abstinence from smoking. Results The log rank test for 6 years (chi(2) = 8.5, P = 0.004) shows a significant association between abstinence from smoking and type of treatment. Sustained abstinence rates for the patch and nasal spray group and patch only group were 51% v 35% after 6 weeks (P = 0.011 (chi(2)), 95% confidence interval 1.17% to 3.32%), 37% v 25% after 3 months (P = 0.045, 1.01% to 3.08%), 31% v 16% after 6 months (P = 0.005, 1.27% to 4.50%), 27% v 11% after 12 months (P = 0.001, 1.50% to 6.14%), and 16% v 9% after 6 years (P = 0.077, 0.93% to 4.72%). Conclusions Short and long term abstinence rates show that the combination of using a nicotine patch for 5 months with a nicotine nasal spray for 1 year is a more effective method of stopping smoking than using a patch only. The low percentage of participants using the nasal spray at 1 year, and the few relapses during the second year, suggest that it is not cost effective to use a nasal spray for longer than 7 months after stopping a patch.