In 1989 and 1990, we isolated five strains of Haemophilus paragallinarum in the Philippines. Serological studies were done on three of these isolates. The results of haemagglutination, reactability to monoclonal antibodies and cross immunization with standard strains showed that they belonged to serotypes A, B and C respectively. This is the first report on the isolation of H. paragallinarum and on a related serological study in the Philippines.