The Biomedical Science Working Group, led by Betsy Herold, MD, provides scientific advice and leadership on several key aspects of MTN research. These include the development of hypothesis-driven secondary objectives in MTN protocols, and consideration of the best approaches for the collection, storage, and evaluation of clinical trial specimens. This group focuses primarily on determining where study products end up in the body (pharmacology), evaluating the causes of possible inflammation (safety), examining potential changes in vaginal bacteria (safety), and investigating HIV-1 genetic changes in study participants who are infected during the course of research, if they occur. The work of this group provides critical input that enables the MTN to implement cutting-edge science in microbicide testing that improves the quality of microbicide trial research data.