The transition from a program that permitted and tacitly approved of smoking to one that prohibited smoking and addressed nicotine dependence as another drug dependency occurred in four phases: (1) making the decision to become smoke-free; (2) preparing for the change; (3) implementing the change; and (4) coping with the results of the change. Data collected between September 1990 and July 1995 on 263 admissions before and 2,182 admissions after the unit became smoke-free revealed that going smoke-free did not affect the incidence of premature discharges or aggressive behaviors and did not change the overall rate of program completion by either smokers or nonsmokers. During the first 3 months after going smoke-free, the program completion rate dropped for both smokers and nonsmokers. By the fourth month, the program completion rate returned to previous levels. After 17 months, the program completion rate was higher than it had ever been. The initial drop in the program completion rate was attributed to the disruption caused by a significant programmatic change and not to the unit's smoke-free status. Further, the increased experience of unit staff in treating nicotine dependence resulted in improved patient outcomes. 67 references, 6 tables, and 1 figure