Histocompatibility antigen typing was carried out in 50 Caucasian patients with primary open-angle glaucoma (POAG) and 50 Caucasian ocular-normotensive subjects. HLA-A 3 was present in 46%, B7 in 52%, B 12 in 50%, and either B 7 or B 12 in 88% of patients with POAG. These prevalences in POAG patients were significantly greater than in ocular-normotensive subjects (p < 0.01, p < 0.0005, p < 0.001, and p < 0.0005, respectively). The prevalences of A 3-B 7, A 3-B 12 and either combination were also significantly greater in POAG patients than in the ocular normotensives (p < 0.005, p < 0.005, and p < 0.0005, respectively). HLA-BW 35 was noted to be in deficit in Caucasian POAG patients (8%) as compared to Caucasian ocular normotensives (32%; p < 0.01).