Aims. The purpose of this study was to determine predictors of smoking cessation from a sample of pregnant Medicaid recipients. Of special interest was whether patient stage of change, based on the transtheoretical model, was predictive of smoking behaviour change during pregnancy. Participants/setting. The sample was drawn from a cohort of pregnant smokers who were participants in a prospective, randomized clinical trial conducted in four public health maternity clinics in Birmingham, Alabama, USA. Design/measurements. The 435 participants entered prenatal care on or before their 24th week of gestation and had saliva collected from cotanine assays at baseline and follow-up. In this secondary analysis, descriptive statistics defined the sample, cross tabulation procedures identified a preliminary set of predictor variables, and discriminant function analyses revealed that patient baseline cotinine value, duration of smoking habit, self-efficacy, exposure to environmental tobacco smoke, and exposure to patient education methods were predictive of non-smoking status assessed during the third trimester of pregnancy.