Penicillium marneffei is a dimorphic fungal pathogen, which can cause disseminated disease both in immunocompetent and immunocompromised patients. The prevalence of disseminated P. marneffei infection has increased markedly over the past few years. This increase is due exclusively to infection among patients infected with HIV. Less than 40 cases of P. marneffei infection were reported prior to the HIV epidemic in southeast Asia, whereas more than 1000 patients have been diagnosed at Chiang Mai University Hospital alone since the beginning of the HIV/AIDS epidemic in northern Thailand. In addition, cases of disseminated P. marneffei infection have been reported in individuals with HIV infection from the United States, the United Kingdom, the Netherlands, Italy, France, Germany, Switzerland, and Australia following visits to the endemic region.