Oral candidiasis is one of the more common infections encountered by man. It manifests itself in a variety of forms, and can arise in any region of the mouth. A generally innocuous and treatable disorder in healthy individuals, it can be the herald of underlying disorders that affect the endocrine or immune systems. In the debilitated or seriously ill, the capacity for seemingly benign oral candidiasis to progress into fulminating fatal infections by hematogenous dissemination must not be ignored. Oral candidiasis in the otherwise healthy patient challenges the physician's ability to identify the contributing factors and associated diseases that predispose to the infection. In the cancer and transplant patient, oral candidiasis is a harbinger of systemic infection, and has become a significant obstacle to successful management of patients with life-threatening diseases. Although several efficacious agents are available for uncomplicated candidiasis, there remains a need for better prophylactic agents to prevent dissemination and better therapeutic agents to treat established infections in immunocompromised patients.