Penicilliosis is caused by Penicillium marneffei, a dimorphic fungus endemic in southeast Asia and southern China. Since 1988, this deep mycosis has been one of the most frequent opportunistic infections in subjects with HIV infection in this region. We report the first observation of penicilliosis in Laos in a subject infected by HIV.A Laotian women with HIV infection and under treatment for tuberculosis, was hospitalized with a cough, fever and cervical lymphadenopathy. A lymph node smear stained with RAL 555 confirmed the diagnosis of penicilliosis. The histologic examination detected some Penicillium marneffei, stained by PAS and Gomori-Grocot. The patient was treated successfully with ketoconazole.Penicilliosis is endemic in southeast Asia. Especially in Thailand, it is a common opportunistic infection in HIV-infected persons. This case confirms the existence of penicilliosis in Laos, where its prevalence as an opportunistic infection is probably underestimated. The diagnostic method (slide stained with RAL 555) used in this case is simple, rapid, and appropriate for countries with limited economic resources to devote to the penicilliosis diagnosis.