We encountered two cases of Harada's disease in monozygotic twins, and this is the first such report as far as could be determined. Case 1 was a 32-year-old woman who presented a typical clinical picture of Harada's disease. Seven years later, case 2 (the younger sister), also presented with the disease at 39 years of age. Case 2 had a transitional diffuse type of Harada's disease, which was possibly due to differences in her treatment. Both patients had papilledema. Since these twins both developed Harada's disease, it is suggested that hereditary factors including HLA type are very important in its development. The HLA type of both these patients was A2, A26, B51, B7, CW7, DR1, and DR4.