Yeasts occur commonly in the oral cavity in healthy individuals. The prevalent species isCandida albicans(about 60–70% of all isolates).C. glabrataandC. tropicaliscome next, followed by otherCandidaspecies 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. albicansis 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. albicanscan 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 inCandidamorphology 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.