Pasteurella multocida serotype B:2 is the causative agent of haemorrhagic septicaemia, a fatal disease of cattle and buffaloes. Formalin inactivated whole cell bacterin is used to prepare vaccines in India. However, outer membrane proteins (OMP s) of P multocida were reported to be potential immunogens. The 87-k D aOMP of P multocidaP 52, serotype B:2 has been identified as one of the major antigens because this protein reacted with serum of vaccinated animals. The gene omp87, encoding an 87-k D a OMP was amplified and cloned into pBluescript SK (–) vector. This gene was found to localise in a 9·0 kb Hind III fragment of P multocida genome.