A "smoke-free" policy was adopted at the Duke University Medical Center but not at the adjacent University Campus. Three months after the smoking prohibition went into effect, a cross-sectional telephone survey was conducted, using randomly selected groups of 400 employees from each campus. Subjects were queried about current and previous smoking histories and their opinion of the smoking ban. As determined retrospectively from this survey, at the time of the announcement of the policy and 6 months before implementation, 23.6% of employees at the Medical Center were smokers, compared with 20.3% on the University Campus. Three months after implementation of the Medical Center smoking prohibition, smoking cessation rates were 12.6% at the Medical Center and 6.9% on the University Campus dating back 9 months to the time of policy announcement (P less than 0.10). Mean cigarette consumption during work hours declined over this same period from 8.1 +/- 6.8 (mean +/- SD) to 4.3 +/- 4.4 at the Medical Center but showed little change on the University Campus (9.3 +/- 7.5 v 8.7 +/- 8.0). Overall, 75.8% of subjects at the Medical Center "somewhat" or "strongly" agreed with the policy compared with 73.2% on the University Campus. A follow-up survey of the cohort of current or recent ex-smokers identified on the initial survey was conducted 6 months later. This survey revealed a smoking cessation rate of 22.5% at the Medical Center and 6.9% on the University Campus, dating back 15 months to the time of policy announcement (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)