Paul Wenzel Geissler teaches social anthropology at the University of Oslo and at the London School of Hygiene and Tropical Medicine. He studied medical zoology in Hamburg and Copenhagen (Ph.D. 1998) and social anthropology in Copenhagen and Cambridge (Ph.D. 2003). Since 1993 he has worked in western Kenya, conducting first medical research and then several years of ethnographic fieldwork. Currently he is writing an ethnography of post-colonial scientific research in Kisumu, Kenya. After studying social anthropology in London and Copenhagen, Ruth Jane Prince is presently Smuts Fellow at the Centre of African Studies, University of Cambridge. She has conducted ethnographic fieldwork in western Kenya since 1997 focusing on medical anthropology, kinship and Christianity. Her current research deals with HIV interventions and antiretroviral treatment programmes in Kenya, and related issues of global health, the political-economy of knowledge, transnationalism and the state.