Penicilliosis marneffei, a common mycosis among AIDS patients living in Southeast Asia, has been recently suggested for inclusion in the AIDS surveillance case definition. Infections with Penicillium marneffei were rare in the past, but infections with this dimorphic fungus have increased with the endemic of AIDS in the region. The reservoir of P. marneffei in nature is still unknown, although it seems likely that inhalation may be the route of entry of the organism leading to infection in humans. P. marneffei can cause two clinical types of the disease; focal and fatal progressive, disseminated infections, characterized by a variety of symptoms which can mimic those of other diseases. Oral P. marneffei lesions usually occur in patients with disseminated infections, presenting as shiny papules, as erosions or as shallow ulcers covered with whitish yellow, necrotic slough which may be found on the palate, gingiva, labial mucosa, tongue and oropharynx. Biopsy and culture provide definitive diagnoses, while serologic tests for both antibody and antigen are useful in rapid presumptive diagnoses as well as in surveillance studies of the prevalence and latency of the infection. Penicilliosis marneffei is a treatable disease, but late diagnosis and treatment may be fatal. Itraconazole and ketoconazole are the drugs of first choice for mild to moderately severe forms of the disease, whereas parenteral therapy with amphotericin B may be required for seriously ill patients. Recurrence of the disease is common, therefore maintenance is recommended. As reported, prophylaxis generating resistant strains are likely to develop.