PURPOSE: To compare in eyes of black and white patients the progression of glaucoma after failure of medical therapy and upon start of surgical intervention. • DESIGN: Cohort study analysis of data from a randomized clinical trial. • METHODS: This multicenter study included open-angle glaucoma patients who had failed medical therapy: 451 eyes of 332 black patients, 325 eyes of 249 white patients. Eyes were randomly assigned to an argon laser trabeculoplasty (ALT)-trabeculectomy-trabeculectomy (ATT) sequence or a trabeculectomy-ALT-trabeculectomy (TAT) sequence; they had been followed for 7 to 11 years at database closure. Main outcome measures were decrease of visual field (DVF), sustained decrease of visual field (SDVF), decrease of visual acuity (DVA), sustained decrease of visual acuity (SDVA), and failure of first surgical glaucoma intervention. Statistical methods included logistic regression to obtain average adjusted black-white odds ratios for binary outcomes, and Cox regression to estimate adjusted black-white risk ratios for time-to-event outcomes. • RESULTS: In the ATT sequence blacks were at lower risk than whites of failure of first intervention (ALT, RR = 0.68, P = 0.040). In the TAT sequence blacks were at higher risk than whites of failure of the first intervention (trabeculectomy, RR = 1.79, P 5 0.033), of intraocular pressure ≥18 mm Hg (average OR = 1.41, P = 0.026), and of DVF (average OR = 1.78, P = 0.007). In both treatment sequences, the average number of prescribed medications was greater for blacks than whites (P ≤ 0.002). • CONCLUSIONS: The results support the hypothesis that after failure of medical therapy and upon initiation of surgical intervention, an initial intervention with trabeculectomy retards the progression of glaucoma more effectively in white than in black patients. The data provide a weak suggestion that an initial surgical intervention with ALT retards the progression of glaucoma more effectively in black than in white patients.