OBJECTIVES: This study assessed the effectiveness of a smoking cessation program for women in public health clinics, controlling for reported exposures to 4 common intervention components (provider advice, booklet, video segment, posters) among smokers in the control group. METHODS: After a baseline control period, 10 pair-matched clinics were randomly assigned to study groups. A total of 1042 smokers in the combined baseline and control groups and 454 smokers in the intervention group completed a preintervention questionnaire and a postintervention telephone interview 5 to 8 weeks later. Eight smoking outcomes, including quitting, were analyzed for the effect of reported exposure to intervention components, experimental program, and clinic service. RESULTS: Greater exposure to intervention components, being in the experimental program, and being seen in prenatal clinics independently improved smoking outcomes. CONCLUSIONS: The number of interventions reported by smokers in the control group ranged from none to 4 and varied across clinic services. The experimental program we tested produced better outcomes than the minimal smoking cessation interventions already existing in the control clinics, after we controlled for whether smokers were or were not exposed to these interventions.