Purpose: To determine the change in intraocular pressure (IOP) and ocular hypotensive medication use after cataract extraction in the Medication Group of the Ocular Hypertension Treatment Study. Design: Secondary analysis of randomized clinical trial data. Methods: We included 92 participants (n = 149 eyes) of the Medication Group of the Ocular Hypertension Treatment Study who underwent cataract surgery in at least 1 eye during the study and 531 participants (n = 1004 eyes) of the Medication Group who did not undergo cataract surgery. We defined the “split date” as the first study visit that cataract surgery was reported for the cataract surgery group and the 15th visit in the control group to equalize the median number of visits. We then compared the 2 groups at visits relative to this split date. Main outcome measures: Difference in preoperative and postoperative IOP, and number of classes of ocular hypotensive medications between the cataract and control group over a 72-month period. Results: Cataract surgery significantly decreased the number of ocular hypotensive medications at all postoperative visits (mean, −0.4 medications; P ≤ .005) through the 48-month postoperative visit when compared with the control group. At the split date, approximately 23% of eyes were medication free and 41% had a reduced medication burden. Cataract surgery resulted in a decrease in IOP (P < .001), but the difference in IOP between the groups reduced over time and became nonsignificant after 12 months. Conclusions: Cataract surgery in patients with ocular hypertension produced sustained reductions in the average number of ocular hypotensive medications and transient reductions in IOP.