We have carried out an open multicenter follow-up study of the efficacy of a smoking cessation therapy that combined psychological support with use of a nicotine nasal spray. Fifty-seven subjects (37 men, 20 women) with a mean age of 40.3 +/- 15.7 yr and smoking 37.4 +/- 4.7 cigarettes per day were enrolled. The mean Fagerström test score was 8.9 +/- 1.1. Patients received minimal psychological support and were prescribed a nicotine nasal spray at the recommended dose of 1 to mg/h for use while awake for a period of three months, with gradual reduction of dose. Subjects were seen on six occasions (on the first day of consultation; 1, 2 and 6 weeks after quitting; 3 and 6 months after quitting). After three months of follow-up, 22 patients (39%) were abstinent; six months after first trying to quit, only 20 of the 57 enrolled had succeeded (35%). Although most subjects (over 90% in the first 15 days, and over 50% at three months) used the treatment, only a small percentage (3%) followed the appropriate doses in the first 15 days and 31% reported doing so at the three-month check-up. The mean score reflecting withdrawal syndrome tripled over baseline level during the first six weeks of follow-up. Over three quarters of the subjects suffered side effects caused by the spray, the most common being nasal irritation, rhinorrhea and tearing. Five patients (87%) lef the study because of intolerance to medication. In conclusion, our study found a rate of success of 35% after six months of follow-up. Use of the prescribed medication was inadequate; withdrawal syndrome was more intense and the prevalence of side effects increased during the early treatment period.