Yeasts occur commonly in the oral cavity in healthy individuals. The prevalent species is Candida albicans (about 60-70% of all isolates). C. glabrata and C. tropicalis come next, followed by other Candida species and genera (Rhodotorula, Saccharomyces, etc.) which are all of rare occurrence and transient. The yeast flora increases in many patient groups, especially those who are immunocompromised. C. albicans is the most important species, being the cause of almost all cases of yeast infections in the region, often in association with other species. The number isolated from the oral cavity depends on testing site and methods used. C. albicans can be typed by means of serology (types A and B), by biotyping, by morphology, by means of sensitivity to killer factors, by electrophoretic karyotyping, DNA fragments, and immunoblotting. Such methods may be of value epidemiologically. Switching in Candida morphology is associated with changes in micromorphology and physiology. Several non-yeast fungi may affect the oral cavity, most frequently in association with lung or disseminated infections.