Objective: To compare the intraocular pressure (IOP) responses of self-identified African American and white participants in the Ocular Hypertension Treatment Study to therapeutic trials of topical, nonselective β-adrenergic antagonists or prostaglandin analogues. Methods: Multivariate models that adjusted for baseline IOP and corneal thickness were used to estimate IOP response by race. Participants included 536 who were prescribed topical β-adrenergic antagonists and 191 who were prescribed prostaglandin analogues, 25% of whom were African American. Main Outcome Measure: Intraocular pressure response in the ipsilateral eye after 4 to 6 weeks of a therapeutic trial. Results: Intraocular pressure response to nonselective β-adrenergic antagonists did not differ between African American and white participants. Intraocular pressure response to prostaglandin analogues was slightly greater in African American participants, but this difference was not statistically significant. With both classes of medication, greater IOP reduction was associated with higher baseline IOP and thinner central corneal measurement. Conclusions: We found no statistically significant differences in IOP response to topical, nonselective β-adrenergic antagonists or prostaglandin analogues between self-identified African American and white individuals. Application to Clinical Practice: Studies of IOP response to medication should statistically adjust for baseline IOP and central corneal thickness. Clinicians should consider factors other than ethnicity when choosing an ocular hypotensive medication for a patient. Trial Registration: clinicaltrials.gov Identifier: NCT00000125.