To elucidate the family history of glaucoma (FHG) as a risk factor for ocular hypertension(OH) vs glaucomatous optic nerve damage, we reviewed the clinical records of 361 primary open-angle glaucoma(POAG) patients, 178 OH subjects, and 927 normal controls randomly selected from an urban medical center eye clinic. The prevalence of a positive FHG was 27% in the POAG patients, 47% in the OH subjects, and 11% in the normal controls. Whereas a positive FHG was a significant risk factor for both OH and glaucoma compared to normal control subjects (OR = 7.56, 95% CI: 5.27-10.85, P < .0001 for OH; OR = 3.15, 95% CI: 2.31-4.31, P < .0001), it was a risk factor more significantly for OH than for glaucoma being significantly more prevalent in OH than in POAG (OR = 2.40, 95% CI: 1.65-3.49, P < .0001). These results suggest the importance of additional risk factors other than IOP for glaucomatous optic nerve damage.