Eales' disease is a primary retinal perivasculitis of an undetermined etiology seen predominantly in the Indian subcontinent and rarely in the West. Strong HLA association has been proven in retinal vasculitis of Behcet's disease. HLA association of Eales' disease is unknown and therefore the present study was undertaken to determine the same. The frequency of 30 HLA antigens (9 HLA-A antigens, 10 HLA-B antigens, 3 HLA-C antigens, 7 HLA-DR antigens and 1 HLA-DQ antigen) was studied by standard micro-lymphocytotoxicity test in 57 patients with Eales' disease and 50 age and sex-matched normal persons as controls. Both the patients and controls underwent complete ocular and clinical examinations and laboratory investigations. Inflammatory diseases similar to Eales' disease were ruled out in the patients before they were enrolled. Statistically significant higher phenotype frequencies of HLA B5 (B51), DR1 and DR4 were observed among patients with Eales' disease as compared to controls. The gene frequency of HLA B5 (B51) in our group of patients and controls was comparable with other earlier studies in the Indian population. The finding of significant association of Eales' patients with positive disequilibrium ( ) haplotypes A3-B44 and A11-B12 may be related to the development of this disease. The presence of the above HLA antigens may be indicative of predisposition to Eales' disease.