[Vitamin A supplementation among HIV-positive pregnant women in Burkina Faso: knowledge, practices, and factors associated with provision of supplements]. To examine the determinants of vitamin A supplementation among HIV-positive pregnant women. A sample of 993 HIV-positive women attending antenatal clinics in Ouagadougou and Bobo-Dioulasso (Burkina Faso) were included. Mothers were interviewed about their knowledge of vitamin A, their knowledge of the benefits of vitamin A supplementation to prevent mother-to-child transmission (MTCT) of HIV, and the factors associated with provision of vitamin A supplementation to their child. Almost all of the 993 women interviewed (99%) reported knowing about vitamin A, and 90% were aware of the role of vitamin A in the prevention of MTCT of HIV. However, only 22% knew that vitamin A is given orally and only 10% knew that vitamin A can be given to infants from birth up to 6 months. About 35% of women did not know the number of days a child needs to receive vitamin A. Four hundred and fifty-four of the 993 women interviewed reported having given vitamin A to their child. Women who were unaware of the benefits of vitamin A for their own health were less likely to be aware that their child should receive vitamin A (OR= 0.59; 95% CI 0.36-0.97). Women who did not know that vitamin A can be given to an infant until 6 months of age were less likely to give their child vitamin A at birth (OR=0.60; 95% CI 0.37-0.97). The major reasons for not giving vitamin A were forgetting (53%) and lack of money to purchase it (41%). Vitamin A supplementation programs should include the importance of vitamin A to prevent MTCT of HIV in pregnant women. These programs should also include ways to disseminate information on vitamin A to HIV-positive women and ways to make vitamin A accessible.