The eyes obtained from two Japanese autopsy cases of patients with Vogt-Koyanagi-Harada disease were immunohistochemically examined. Both patients, a 63-year-old woman and a 68-year-old man, were clinically and histologically diagnosed as having Vogt-Koyanagi-Harada disease. Immunohistochemically, the choroidal infiltrate was composed predominantly of T lymphocytes with a larger proportion of helper/inducer T cells than suppressor/cytotoxic T cells and it also included activated lymphocytes expressing CD26 and CD25 antigens. Class II major histocompatibility complex was expressed in the choroidal melanocytes as well as in the endothelium of the choriocapillaris. Depositions of complement, however, were focally noticed in the choroid. Our results indicate that the cell-mediated immune process plays an important role in the development and progression of Vogt-Koyanagi-Harada disease, while choroidal melanocytes appear to play a pathogenic role in this disease.