In response to an increasing prevalence of sexually transmitted diseases, especially AIDS, efforts to prevent further infections have been heightened. One of those approaches has been the development of topical microbicidal agents or microbicides. These are compounds designed to protect the body's mucosal surfaces from infection by sexually transmitted disease-causing pathogens. Numerous candidates are currently in preclinical stages; however, only a handful have been tested for safety, and even fewer are ready for clinical efficacy trials. In this update, we describe some of the specific features of microbicide research and development, including preclinical screening algorithms, candidate's ideal properties, examples of compounds presently in the pipeline, and future prospects.