Background:Immunization of rabbit against Staphylococcus aureus type 5 did not increase antibody titer significantly in previous study. We proposed that lack of protection is due to low immunogenicity of this bacterium and a suitable adjuvant is needed to augment antibody production against it. In this study the effect of aluminium hydroxide [Al(OH)3], Freund's adjuvant and DTP vaccine on immunization of rabbit against encapsulated S. aureus type 5 by agglutination method was considered.Methods:30 male New Zeeland white rabbits (4-6 months) were grouped in 6. They were injected intramuscularly using suspension of killed encapsulated S. aureus type 5 (strain Reynolds) with and without adjuvant. The last two groups were injected DTP vaccine and saline alone. Injections were done three times within 21 days intervals; blood sample was obtained from marginal ear vein before every injection and 21 days after the last injection and sera were collected in -20ºC. Agglutination method was employed for detection of antibody titer.Findings:Immunization of rabbits to encapsulated s. aureus type 5 with Al(OH)3, Freund's adjuvant and DTP vaccine showed rise in antibody titer against it. Mean antibody titer of immunized rabbits with DTP vaccine after the third injection was more than those immunized with Al(OH)3 and Freud's adjuvant (p=0.049). Also mean antibody titer in rabbits immunized with Freund's adjuvant was more than those immunized with Al(OH)3 but this difference was not significant (p=0.27).Conclusion:In this study, DTP vaccine induced higher antibody titer against encapsulated S. aureus type 5 than Al(OH)3 and Freund's adjuvant. Therefore, it is suggested that DTP vaccine may be used as an adjuvant with suspension of killed encapsulated S. aureus type 5 in rabbit.Key words:Encapsulated staphylococcus aureus, adjuvant, aluminium hydroxide, Freund, DTP vaccine