An immunological basis for neurological involvment in Vogt-Koyanagi-Harada syndrome was sought by means of the migration-inhibition factor technique with human myelin basic protein. The test was carried out in 4 patients who had recent manifestations of the syndrome, 2 of whom were evaluated before and after initiation of steroid treatment; in 1 patient 4 yr after recovery from the syndrome; in 3 patients having uveitis of other causes; and in 12 healthy controls. The results were positive in all 4 patients who had recent manifestations, whereas they were negative in all the others. This finding may constitute evidence of a cell-mediated immunity toward components of the nervous system in this disease entity.