This paper explores the ways in which young South African school children (aged between seven and eight) in a predominantly white primary school give meanings to HIV/AIDS. Using ethnographic methods and interview data, the analysis of young children's responses shows that their accounts of HIV/AIDS draw from their knowledge of disease more generally and associate it with allergies, fungus, moss as well as contagion. Their knowledge is also intricately connected with their understandings of sex and gender. Within the same age group young children's knowledge of the disease vacillates from inaccurate information to graphic accounts of sex as a transmission route and gendered vulnerability to the disease. The findings of this study suggest that children are active makers of meanings about the disease. They relate HIV/AIDS to disease, to contagion and dirt, and in doing so harness social processes including race, class, sex and gender. Efforts to scale up young children's understanding of the disease in the early years of primary schooling are significant in the light of this study.