How can pregnant women be helped to stop smoking? This was a pilot study of midwife home-based motivational interviewing. Clients were 100 consecutive self-reported smokers booking at clinics in Glasgow from March to May 1997. Smoking guidance is routinely given at booking. In addition, intervention clients received a median of four home-based motivational interviewing sessions from one specially trained midwife. All sessions (n = 171) were audio-taped and interviews (n = 49) from 13 randomly selected clients were transcribed for content analysis. Three 'experts' assessed intervention quality using a recognized rating scale. Cotinine measurement on routine blood samples confirmed self-reported smoking change from late pregnancy telephone interview. Postnatal telephone questionnaire measured client satisfaction. Focus groups of routine midwives explored acceptability, problems and disruption of normal care. Fisher exact, chi 2 and Mann-Whitney tests compared enrolment characteristics. Two-sample t-tests assessed outcome between groups. Motivational interviewing was satisfactory in more than 75% of transcribed interviews. In this pilot study, self-reported smoking at booking (100 of 100 available) corroborated by cotinine (93 of 100) compared with late pregnancy self-reports (intervention 47 of 48; control 49 of 49) and cotinine (intervention 46 of 48; control 47 of 49) showed no significant difference between groups. Tools have been developed to answer the question: 'Can proactive opportunistic home-based motivational interviewing help pregnant smokers reduce their habit?'.