AIM: To investigate whether maternal smoking remains associated with decreased breastfeeding duration after adjustment for the mother's infant feeding intention. METHOD: Pregnant women resident within Avon, UK, expected to give birth between 1 April 1991 and 31 December 1992 were recruited in a longitudinal cohort study. Main outcome measures included maternal infant feeding intention at 32 wk of pregnancy: intention for the first week, intention for the rest of the first month and intention in months 2 to 4. Maternal smoking was defined as any smoking reported at any time during pregnancy. Data on initiation and duration of breastfeeding were based on the questionnaire at 6 mo postpartum, supplemented by data from the 15-mo questionnaire if necessary. RESULTS: Women who smoked during pregnancy had an adjusted odds ratio of 1.5 (95% CI: 1.3-1.7) of not breastfeeding at 6 mo compared to non-smokers (adjusting for maternal age, education and intention). Survival analysis of duration of breastfeeding in the first 6 mo postpartum found that women who intended to breastfeed for less than 1 mo were 78% more likely to stop at any given time than women planning to breastfeed for at least 4 mo, while smokers were 17% more likely to stop breastfeeding than non-smokers. CONCLUSION: Although women who smoke are less likely to breastfeed their infants than are non-smoking women, it appears that this is largely due to lower motivation to breastfeed rather than a physiological effect of smoking on their milk supply.