The health benefits of breastfeeding to infants and mothers have been well recognised. This study applies linear regression analysis to assess the determinants of breastfeeding duration of first born using data from the Second Malaysian Family Life Survey. The proportion of women who breastfed their first child is 82 percent, of which 97 percent reported their breastfeeding duration. The distribution of breastfeeding duration has a mean of 5.7 months and a median of two months. Important determinants of breastfeeding duration include maternal age, ethnicity, period of first birth, husband's occupation and work status of the woman.