Researchers and sponsors are required to assist HIV prevention trial participants to remain HIV-uninfected by ensuring access to prevention services. Ethics guidelines require that these HIV risk-reduction services be state of the art. This and related ethics recommendations have been intensely debated. This descriptive study aimed to identify actual HIV prevention practices for two HIV vaccine trials at five South African sites, to explore whether actual practices meet guideline recommendations and to discuss implications for practices and ethics guidelines. Practices were (...) examined through a review of site documents and interviews with site staff and network representatives, as well as community advisory board and research ethics committee representatives. A thematic analysis of HIV prevention practices, perspectives and perceived challenges was undertaken. Findings indicated that there was a high degree of correspondence between actual practices in South African HIV vaccine trials and guideline recommendations. Key challenges for implementing prevention services were identified as partnerships, provider-promotion of services and participant uptake of services. Practices deviated most from guidelines with regard to the description of prevention plans in informed consent forms. Recommendations are made for both practices and ethics guidelines. (shrink)