Microbicides are the new frontier of products for the prevention of sexually transmitted infections (STIs). Twelve years ago, scientists realized that existing spermicides had some anti-microbial activity and perhaps could be improved or reformulated with new compounds to provide a complete barrier against STIs. However, the development and successful marketing of an effective, non-toxic, convenient and affordable vaginal microbicide that women can use on a long-term basis hinges on a close collaboration between research institutions and the pharmaceutical industry. The Population Council has recently taken the first step in instituting a multifaceted strategy for the development of a microbicide by establishing the Microbicide Basic Science Network, comprising of scientists with diverse backgrounds and expertize.