A family history of glaucoma was found in 50% of patients with primary open-angle glaucoma (POAG) and 43% of patients with ocular hypertension (OH). Positive family history was twice as prevalent in those with OH and either HLA-B7 or B12 antigens than in OH with neither antigen (P less than .01). Although POAG occurred equally in men and women, the prevalence of a positive family history of glaucoma on the maternal side of the family in POAG patients was six to seven times greater than on the paternal side (P less than .0005). However, in patients with OH, but no glaucomatous field loss, there was no difference in prevalence of maternal and paternal family history. Even in OH with HLA-B7 or B12 antigens, there was no predominance of maternal family history. The implication that offspring were more likely to develop POAG when their mother's side of the family rather than their father's side had the disease has provided an additional potentially useful risk factor in patients with OH. In addition, it has raised interesting questions as to possible maternal cytoplasmic factors in the transmission and pathogenesis of POAG.