 HIV infected women will be counselled according to the WHOUNICEFUNAIDS infant feeding guidelines. All HIV-infected women and a random sub-sample of HIV-uninfected women will be recruited antenatally. Those who choose to breastfeed will be visited frequently at home by a team of breastfeeding counsellors before and after delivery to promote and support EBF. HIV-infected mothers who choose not to breastfeed will be supported in their choice by clinic-based staff. An independent team of field monitors will collect data weekly on feeding practices and morbidity of all infants at home visits. Blood samples will be collected by fingerheel prick and stored on filter paper prior to qualitative and quantitative estimation of HIV viral content to determine the timing of transmission. 