Measles is frequently complicated with pneumonia that could be fatal in numerous occasions. However, a prompt and precise diagnosis of measles is not easily made particularly in the early stage of the disease, or in immunocompromised individuals because of the lack of typical clinical features or the defect in antigen-specific antibody production. In the present paper, we describe a 27-yr-old male who developed fever, skin rash typical of measles, and diffuse pulmonary infiltrates associated with respiratory failure. Infection of lung cells with measles virus was proved by detection of viral genome ribonucleic acid within alveolar macrophages and lymphocytes recovered by bronchoalveolar lavage using reverse transcription-polymerase chain reaction amplification. These techniques may offer a useful tool to make the swift and precise diagnosis of measles pneumonia, thus allowing appropriate therapeutic approaches to the disease.