SUMMARY. Twelve cases of chronic hyperplastic candidiasis of the oral mucosa are described.

Clinically the lesions could not be reliably differentiated from “leukoplakia” due to other causes. All but 2 of the patients were otherwise healthy.

The histological appearances were distinctive: there was invasion by hyphae of C. albicans of the superficial epithelium of an acanthotic and parakeratotic plaque, associated with a characteristic intraepithelial inflammatory reaction.

In 9 cases the antibody titres to C. albicans in serum and saliva supported a diagnosis of candidiasis.

The response of the lesions to oral Nystatin was good in 3 cases and incomplete in 4.

The evidence that C. albicans plays an essential causative rather than a secondary role is critically discussed.

Recognition of chronic hyperplastic candidiasis from other “leukoplakias” is of practical importance since this condition is potentially reversible by medical treatment.