This stduy was carried out to investigate the effects of Isoimmunization by sperm and seminal plasma on density of immunoglobulins in reproductive tract fluids and serum of immunized rabbits. The results obtained were summarized as follows: 1. Antibody titers against sperm and seminal plasma antigen ranged from 8 to 64 to 512, respectively. 2. All immunoglobulins; IgG, IgA and IgM were detected with Indirect ELISA method in the uterine and oviductal fluids as well as the sera of immune rabbits. 3. Concentrations of IgGs in the uterine and oviductal fluids of rabbits immunized with sperm and seminal plasma were higher than those of the control rabbits, but not showed any differences in sera. 4. Amount of IgA in the sera and oviductal fluids of control animals was more than that of the immune animals, while that of IgA in the uterine fluids of control and seminal plasma-immunized animals was higher as compared to sperm immune animals. 5. Average concentration of IgM in the uterine fluids of control and seminal plasma-immunized rabbits was higher than that of sperm-immunized ones. In the oviductal fluids, average concentrations of IgM of immune rabbits was higher than that of immune rabbits.