Using RT-PCR, we can detect measles virus hemagglutinin gene (H gene) of 635bp length directly from measles vaccine strain Shanghai-191, Edmonston strain, nasopharyngeal aspirates and throat swabs of the measles patients. The primers of RT-PCR based on H gene sequence of measles virus did not give the same products from rubella virus and influenza viruses (A1, A3, B). By second PCR amplification, the minimum quantity of measles virus required to give a positive signal was<0.01TCID50. Since the IgM antibody positive rate in early stage of measles patients is always low, the specificity and sensitivity of RT-PCR method may help diagnosing measles cases.