Fungal infections, including candidosis, now pose a serious threat to certain groups of patients particularly the immunocompromised and transplant patients. This chapter describes the work carried out by the authors and presents results from their own in vivo studies as a stepping stone towards a more detailed evaluation and correlation of in vitro and in vivo effects. It is hoped that these studies will be ultimately of practical value in attempts to control and prevent candidosis. Work on the inhibition of candidal adherence to murine vaginal mucosa in vivo was initiated by P. B. Segal et al. These workers demonstrated that treatment of the vaginas of mice before yeast inoculation with either the Candida cell wall component chitin; or its constituent N-acetylglucosamine (NAG); or its derivative, blocked the attachment of C. albicans to the vaginal mucosal surface and thereby prevented vaginal infection.