In recent decades there has been a marked rise in both the labour market participation of women with infants and transcultural marriage in Taiwan. The objectives of this study were to explore the combined effect of employment status and transcultural marriage on the prevalence and factors relating to initiation and continuation of breast feeding in Taiwan. We used multistage stratified systematic sampling to recruit 2048 postpartum women from the Taiwan National Birth Registration database for the period November to December 2003. They were interviewed at home within 6 months of delivery using a structured questionnaire; 87% of the sampled population completed the interview. We used logistic regression analysis to estimate the odds ratio (OR) of breast-feeding initiation and Cox regression (survival) analysis to predict continued breast feeding. The prevalences of initial breast feeding for employed Taiwanese mothers, unemployed Taiwanese mothers, employed foreign-born mothers and unemployed foreign-born mothers were 84.4%, 83.7%, 79.1% and 79.7%, respectively. Among the four groups of mothers who initiated breast feeding, 12.9%, 27.2%, 14.7% and 39.7% of their infants, respectively, were still breast feeding at the age of 6 months. Factors associated with initiation of breast feeding were high maternal education (OR 3.80; 95% confidence interval [CI] 1.81, 7.98) and normal spontaneous delivery (OR 1.36; 95% CI 1.04, 1.78). The main reason for not breast feeding in 52% of the mothers was insufficient or no milk. There existed a combined effect of employment status and transcultural marriage on the continuation of breast feeding. Employed Taiwanese mothers were earlier than others at weaning. Unemployed foreign-born mothers breast fed the longest [hazard ratio (HR) 0.54; 95% CI 0.42, 0.70]. Other factors related to late weaning were high maternal education (HR 0.67; 95% CI 0.47, 0.96), older maternal age (HR 0.76; 95% CI 0.61, 0.94), mother sleeping with baby at night (HR 0.68; 95% CI 0.59, 0.78), and no supplemental baby food before the age of 6 months (HR 0.78; 95% CI 0.68, 0.90). The initiation of breast feeding was high but it decreased dramatically after the postpartum period in Taiwan. There was a significant combined effect of employment status and transcultural marriage on the continuation of breast feeding. Employment is a persistent barrier to continued breast feeding.