Penicillium marneffei, a dimorphic fungus that is endemic in southeast Asia, causes deep-seated infection in humans and rodents. About 20 cases have been reported among the local populations of China, Thailand, and Hong Kong, and 35 cases have now been described in patients infected with the human immunodeficiency virus (HIV). We present a review of the literature and report two additional cases. Both immunocompromised and apparently immunocompetent hosts tend to develop disseminated, symptomatic infection. HIV-infected patients having travelled to southeast Asia and presenting with fever, skin lesions, hepatomegaly, adenopathies, or lung disease should be investigated for Penicillium marneffei infection. The diagnosis is based on the demonstration of the organism in clinical specimens. Treatment with amphotericin B or itraconazole is generally successful, but maintenance therapy is warranted for patients with an underlying immunodeficiency.