Montanide ISA 50 was used as an adjuvant for preparation of inactivated IB vaccines and com-pared with commercially available inactivated LB vaccine adjuvanted with paraffin oil. The vaccine was tested for safety and potency. Serological tests were carried out to follow up the immune status post vaccination by using serum neutralization test and ELISA test for 6 months post vaccination. The results indicated that the vaccine prepared with Montanide ISA-50 oil adjuvant appeared to be more potent and gave protective level reached up to 6 months in comparison with the commercially used vaccine contained paraffin oil gave protection until 4 months only.