The dimorphic yeast, Candida albicans is both a human pathogen and a commensal organism, occupying many niches in and on the human body. Discovery of new metastable morphological states of the organism has led to the hypothesis that its polymorphic nature is related to pathogenesis. Furthermore, these polymorphic states may mask epidemiological relationships in clinical isolates. This project is designed to understand the mechanism of switching between morphological states and to provide DNA sequence markers that will identify particular strains of various Candida species and permit predictive diagnosis for drug sensitivity and other aspects of pathogenesis.