In REACH3 (ClinicalTrials.gov identifier: NCT03112603), ruxolitinib was investigated versus best available therapy (BAT) for 3 years in patients with steroid-refractory/dependent chronic graft-versus-host-disease (SR/D-cGVHD). Patients received ruxolitinib (10 mg twice daily) or BAT for 24 weeks; thereafter (weeks 24-156), patients continued randomized treatment, entered long-term survival follow-up, or crossed over from BAT to ruxolitinib. In 329 randomly assigned patients (ruxolitinib: 165; BAT: 164), the median failure-free survival (FFS) was 38.4 months for ruxolitinib versus 5.7 months for BAT (hazard ratio, 0.36 [95% CI, 0.27 to 0.49]). Median duration of response (DOR) was not reached for ruxolitinib versus 6.4 months for BAT. Ruxolitinib-treated patients had a higher probability of FFS (ruxolitinib: 56.5%; BAT: 18.2%) and maintaining a response (ruxolitinib: 59.6%; BAT: 26.7%) at 36 months. Median overall survival was not reached. Nonrelapse mortality and malignancy relapse/recurrence events were low. In 70 patients who crossed over to ruxolitinib, the overall response rate (50.0%) at week 24 and best overall response (81.4%) during the crossover period were consistent with the primary analysis of randomly assigned patients. No new safety signals were observed. Ruxolitinib provided longer FFS and DOR than BAT, demonstrating sustained efficacy and manageable safety over 3 years of follow-up in patients with SR/D-cGVHD.