To investigate the risk factors for glaucoma, we reviewed the clinical record of 361 primary open-angle glaucoma (POAG) patients, 178 ocular hypertensives (OH), and 927 controls without POAG or OH, randomly selected from an urban medical center eye clinic. Old age defined as > or = 55 year, (odds ratio ratio (OR) = 3.13 95% confidence interval (CI): 2.06-4.76, P < .0001), black race (OR = 2.58, 95% CI: 1.79-3.74, p < .0001), hypertension (OR = 1.709, 95% CI: 1.15-2.51, P < .0108), and diabetes mellitus (OR = 1.83, 95% CI: 1.08-3.09, P = .0308) were identified as significant risk factors in POAG compared to OH. Old Age (OR = 4.94, 95% CI: 3.62-6.76, p < .0001), and black race (OR = 2.04, 95% CI: 1.59-2.61, P < .0001), HTN (OR = 1.63, 95% CI: 1.26-2.11, P = .0002), and DM (OR = 1.40 95% CI: 1.02-1.92 P = .0450) were also significant risk factors when compared to normal controls. However, when the 361 POAG patients were compared to 361 controls matched with respect to age, race, and sex, hypertension and diabetes mellitus did not appear to be independent risk factors. Family history of glaucoma was found to be a risk factors more significantly for OH (OR = 6.79, 95% CI: 4.39-10.50, P < .0001) than for POAG (OR = 2.83, 95% CI: 1.90-4.21, P < .0001) compared to the matched control subjects. The apparent importance of hypertension and diabetes as risk factors for POAG may therefore be due at least in part to a higher prevalence of hypertension and diabetes mellitus in the elderly than the young and also in the black race as risk factors for glaucoma may be in part due to an increased prevalence of hypertension and diabetes mellitus in the elderly and blacks. Positive family history of glaucoma appears to be a risk factor more specifically for elevated intraocular pressure than for glaucomatous visual field defects.