Tested transtheoretical model of change positing stages through which smokers move as they successfully change their smoking habit. Subjects in precontemplation (n=166), contemplation (n=794), and preparation (n=506) stages were compared on smoking history, 10 processes of change, pretest self-efficacy, decisional balance, and one- and six-month cessation activity. Results strongly support the stages of change model. (Author/NB)