ABSTRACT Pathogenic fungi are capable of switching between different phenotypes, each of which has a different biological advantage. In the most prevalent human fungal pathogen, Candida albicans , phenotypic transitions not only improve its adaptation to a continuously changing host microenvironment but also regulate sexual mating. In this report, we show that Candida tropicalis , another important human opportunistic pathogen, undergoes reversible and heritable phenotypic switching, referred to as the “white-opaque” transition. Here we show that N -acetylglucosamine (GlcNAc), an inducer of white-to-opaque switching in C. albicans , promotes opaque-cell formation and mating and also inhibits filamentation in a number of natural C. tropicalis strains. Our results suggest that host chemical signals may facilitate this phenotypic switching and mating of C. tropicalis , which had been previously thought to reproduce asexually. Overexpression of the C. tropicalis WOR1 gene in C. albicans induces opaque-cell formation. Additionally, an intermediate phase between white and opaque was observed in C. tropicalis , indicating that the switching could be tristable.