Candidiasis is, by far, the most common mycotic infection of the human oral cavity. The usually manifested clinical expression of oral candidiasis at all ages from the newborn to the elderly is thrush. Other forms that affect the mouth include acute atrophic candidiasis associated with oral antibiotic therapy, chronic atrophic candidiasis attributable to the wearing of full upper dentures, candidal cheilosis ascribable to perlèche or decreased vertical dimension in the lower third of the face, chronic mucocutaneous candidiasis emanating from a T-lymphocyte deficiency, and candidal leukoplakia. Extensive use of antibiotics and immunosuppressive drugs have greatly increased the number of Candida-induced oral infections. Patients debilitated by irradiation, cancer chemotherapy, organ transplants, diabetes mellitus, and defects in cell-mediated immunity are particularly vulnerable. Fortunately, the vast majority of cases of oral candidiasis are not life-threatening and readily respond to appropriately administered anticandida agents. It must always be remembered, however, that the organism has the capacity to produce fulminating fatal infection by hematogenous dissemination from seemingly innocuous oral infections that serve as a portal of entry to the systemic circulation. Consequently, all oral candidal infections in compromised patients must be treated vigorously and effectively.