To discuss the relationship of Bovine Melanin-Associated Antigen (BMAA) to Sympathetic Ophthalmia (SO) and Vogt-Kayanagi-Harada (VKH) syndrome. BMAA was isolated and purified from bovine iris and ciliary body and MTT method was used to measure the peripheral lymphocyte reactions of SO and VKH syndrome patients to BMAA. 15 cases of SO were included in the SO group with 11 males and 4 females. The average age was 37.5, ranging from 23 to 56 years; 15 patients with VKH syndrome were included in the VHK group with 7 males and 8 females. Their average age was 37.2 years, ranging from 24 to 69 years; 20 normal individuals without ocular and systemic autoimmune diseases were included in the control group. These included 9 males and 11 females, aging from 14 to 28 with an average of 23.8 years. The OD values of each group were as follows: SO controls 0.327+/-0.032; SO+ BMAA 0.490+/-0.758; SO+ PHA 0.5310+/-0.918; VKH controls 0.328+/-0.503; VKH+ BMAA 0.430+/-0.530; VKH+ PHA 0.328+/-0.484; Normal controls 0.304+/-0.267; Normal+ BMAA 0.343+/-0.326; Normal+ PHA 0.477+/-0.598. The average OD values of peripheral lymphocytes to BMAA stimulation in SO patients and normal controls were 0.490 and 0.343 respectively. The difference was statistically significant, P< 0.001; The average OD values of peripheral lymphocytes to BMAA stimulation in SO and VKH syndrome patients were 0.470 and 0.430 respectively. The difference was not statistically significant, P> 0.05. BMAA effectively stimulate the proliferative reaction of peripheral lymphocytes in SO patients and BMAA may act as an antigen and contribute in the pathological process of SO. No difference in proliferative reaction of peripheral lymphocytes was found between SO and VKH syndrome patients after BMAA stimulations and BMAA may be involved in the development of both SO and VKH syndrome.