• Twenty high responders to topical corticosteroids (intraocular pressure > 31 mm Hg after six weeks of topical 0.1% dexamethasone, four times daily) and 20 low responders (IOP < 20 mm Hg) of similar age, sex, race, initial IOP, and facility of outflow were selected. After 24 hours of treatment (two doses) of topical 1% epinephrine hydrochloride, the high corticosteroid responders showed a mean (±SD) corrected decrease in IOP of 3.6 ± 2.0 mm Hg as opposed to 1.8 ± 2.1 mm Hg in the low corticosteroid responders. Within both corticosteroid groups, individuals with the antigen HLA-B12 showed significantly greater decreases in IOP. This suggested that the presence of HLA-B12 was not only associated with increased responses to corticosteroids but also to epinephrine.