We evaluated differences in the results of trabeculectomy surgery in primary open-angle glaucoma in 24 consecutive white glaucoma patients matched to 24 African–American glaucoma patients acting as case controls. One year after surgery we found no statistical difference (p = 0.09, paired t test) in the average intraocular pressure between white (13.4 $pM 3.5 mm Hg) and African–American patients (15.8 $pM 5.0 mm Hg). However, African–American patients had a significantly greater distribution of intraocular pressures (p = 0.04, F distribution test), were taking more glaucoma medicines (1.6 compared with 1.0 for white patients; p = 0.03, Wilcoxon sign rank test), and showed less bleb formation (p = 0.04, Wilcoxon sign rank test). This study suggests that after trabeculectomy, on average, the intraocular pressure in both African–American and white patients may be controlled. However, among different individuals intraocular pressure control may be more inconsistent, require more medicines, and be associated with less bleb formation in African–American than in white patients.