Viral retinochoroiditis was induced experimentally by inoculation of herpes simplex virus into the vitreous body in rabbits. The animals were sensitized systemically using 2 pathogens as antigens (herpes simplex virus and toxoplasma gondii) 3 weeks prior to intraocular inoculation. Serum and intraocular fluid were collected 2 weeks after inoculation. The intraocular fluid antibody titers and quotients for these 2 pathogens were then measured to determine the effects of serum antibodies, which are thought to enter the eyes as a result of destruction of the blood-ocular barrier. Experimental criteria for antibody quotients were also determined. Antibody quotients for the etiological virus (herpes simplex virus) ranged from 2 to 20, with an average of 9.7. Those for toxoplasma gondii, the antibody of which is thought to enter the eye from the blood, were all less than 5 with average of 1.9. From these results, it would seem that when the antibody quotient of a pathogen in more than 6 in the intraocular fluid, it is likely to be an etiological organism, while the possibility of infection is very low when the quotient is under 2. More precise studies are required to identify an etiological pathogen when the quotient is 2-6.