To test the hypothesis that ACAID induction is instrumental in producing the distinctive pattern of retinal pathology that follows anterior chamber inoculation of HSV-1 in BALB/c mice, panels of mice received uniocular anterior chamber, uniocular intravitreal, and bilateral anterior chamber inoculations of HSV-1. It was found that contralateral retinitis developed after the first two routes, and ACAID was induced by all three. Enucleation of eyes inoculated with HSV-1 before 3 days post-inoculation(but not thereafter) prevented both ACAID and contralateral retinitis. Intracameral inoculations of HSV-2 induced vigorous delayed hypersensitivity and failed to incite contralateral retinitis. It is concluded that ACAID induction plays a crucial role in the pathogenesis of contralateral retinitis following anterior chamber inoculation of HSV-1.