Breastfeeding practice is common in Malaysia. However, sustaining the duration of exclusive breastfeeding (EBF) practice for up to 6 months as recommended by World Health Organization (WHO) is a problem for mothers. Numerous factors are associated with this good practice and one of the important ones is the socio-demographic factors. The study examined the association of socio-demographic factors and duration of EBF practice among mothers in Kuching, East Malaysia. A cross-sectional study among 159 mothers of children in the age group of 6-24 months through purposive sampling attending Maternal and Child Health (MCH) clinics in Kuching division was conducted between April and Mei 2009. Data was collected using a set of supervised self-completed questionnaire on EBF practice and mother's socio-demographic factors. Factors related to duration of EBF practice were analysed using logistic regression analysis. 88.1% of mothers reported that they initiated and breastfeed their child exclusively. Only 44.3% of mothers breastfeed their child exclusively till 6 months and the others were not. Being unemployed [