Randomized and controlled. Cigarette smokers with evidence of airways obstruction underwent baseline testing that included spirometric responses to isoproterenol and methacholine and were then randomly assigned to one of three groups: a no intervention or usual care group; a group receiving a smoking cessation program and bronchodilator therapy; a group receiving a smoking cessation program and a placebo bronchodilator. The placebo/bronchodilator therapy was double-blind. The smoking intervention consisted of an intensive 12-session smoking cessation program combining behavior modification and use of nicotine gum, with a continuing five-year maintenance program to minimize relapse. The bronchodilator consisted of ipratropium bromide prescribed three times daily, two puffs per time, from a metered-dose inhaler. All groups were followed yearly for five years. The primary endpoint was the rate of change of FEV1. Respiratory morbidity was a secondary endpoint. Recruitment began in November 1986 and was completed in January 1989. The clinical phase of the trial ended in April 1994. The study continues under contract N01-HR-46002 through September, 2004 for data analysis and dissemination of research results.