The promotion of exclusive breastfeeding for 6 months, followed by rapid transition to alternative food sources may be an important public health approach to the reduction of mother-to-child transmission of HIV through breastmilk. The basic ethical principle of ‘informed choice’ requires that HIV positive women are provided with adequate information about their options. However, information is only one factor that affects their decisions. The objective of this ethnographic study was to identify sociocultural influences on infant feeding decisions in the context of a large cohort study designed to assess the impact of a breastfeeding counselling and support strategy to promote exclusive breastfeeding on postnatal transmission of HIV in African women. Following an initial period of exploratory interviewing, ethnographic techniques were used to interview 22 HIV positive women about their views on infant feeding and health. Interviews were tape-recorded, transcribed and analysed with a text analysis program. Five themes of influences on feeding decisions emerged: (1) social stigma of HIV infection; (2) maternal age and family influences on feeding practices; (3) economic circumstances; (4) beliefs about HIV transmission through breastmilk; and (5) beliefs about the quality of breastmilk compared to formula. The study highlights the role of cultural, social, economic and psychological factors that affect HIV positive women's infant feeding decisions and behaviour.