Purpose: To evaluate the efficacy and safety of arteriovenous sheathotomy surgery to decompress branch retinal vein occlusion (BRVO). Design: Prospective, nonrandomized, comparative interventional trial with concurrent control group. Participants: Twenty eyes with decreased visual acuity secondary to BRVO who underwent vitrectomy and surgical decompression by means of arteriovenous sheathotomy were compared with 20 control eyes (10 observation and 10 laser treated). Intervention: The 20 surgical eyes underwent pars plana vitrectomy and arteriovenous sheathotomy with a microvitreoretinal blade. Of the 20 control eyes, 10 had no intervention (observation), and 10 had grid laser photocoagulation a mean of 9 months after diagnosis. Results: The mean preoperative visual acuity was 20/250 in the surgical group and 20/180 in the control group (statistically similar in the observation group and laser-treated group). The mean 14-month visual acuity was 20/63 in the surgical group and 20/125 in the control group (P = 0.02). Seventy-five percent of the surgical group halved their visual angle compared with 40% of the control group (40% observation vs. 40% laser; P = 0.025). Average lines of visual acuity gained were 4.55 in the surgical group and 1.55 in the control group (P = 0.0226; 1.1 lines in observation group and 2.0 lines in laser group). Conclusions: Surgical arteriovenous sheathotomy to decompress BRVO results in significantly better visual outcomes than a matched control group of observation and laser-treated eyes. A randomized multicenter clinical trial is warranted to determine the efficacy of this procedure. © 2004 by the American Academy of Ophthalmology.