This paper is designed to inform program managers and others who are interested in learning more about human immunodeficiency virus (HIV) and infant feeding but who are not necessarily familiar with all of the technical issues in either of these fields. The paper reviews the major advances in the study of human immunodeficiency virus (HIV) and infant feeding and the policy responses to these findings; describes several design and interpretation issues to take into consideration when reading and comparing research studies on this issue; reports the findings of several studies and mathematical models which have been developed to guide program and policy recommendations on HIV and infant feeding; summarizes what existing studies do and do not reveal about this issue; and recommends areas requiring further research to facilitate adaptation and application of the UNAIDS/UNICEF/WHO guidelines on HIV and infant feeding. (Contains 78 references, 2 boxes, and 2 tables.) (SM)