OBJECTIVE To evaluate the efficacy of primary and secondary (following grid laser photocoagulation) intravitreal triamcinolone acetonide (IVTA) injection for the treatment of macular edema associated with branch retinal vein occlusion (BRVO). METHODS Eyes with macular edema secondary to BRVO and best-corrected visual acuity (BCVA) worse than 20/40 were included. Eyes eligible for Branch Retinal Vein Occlusion Study (BVOS) guidelines received grid laser treatment first. Those that were not improved at least two lines following grid laser or that did not meet those guidelines received 4 mg IVTA injection. The efficacy of IVTA treatment was assessed by analyzing the change in BCVA and reduction in central macular thickness (CMT) measured by optical coherence tomography. Intraocular pressure (IOP) spikes and other complications were recorded. RESULTS The data from 37 eyes were included; in 12 of them IVTA injection was given after grid laser while 25 of them received IVTA as a primary treatment. Mean follow-up was 9.6 +/- 4.5 months. BCVA was 0.06 +/- 0.30 and 0.17 +/- 0.50 in the primary and secondary IVTA injection groups, respectively. In the primary injection group, there was a statistically significant gain in BCVA throughout the follow-up (P < 0.05), while a small increase in BCVA was noted only at the third month visit in the secondary IVTA injection group (P = 0.04). Average CMT were 434.8 +/- 122.1microm and 389.0 +/- 171.9 microm before IVTA injection in the two groups, respectively. In the primary IVTA injection group, CMT decreased at 1 month following IVTA injection and remained statistically significant until the sixth month visit (P < 0.05). In the secondary IVTA injection group, a slight reduction in CMT was noted only in the first month visit (P = 0.02). Pre-IVTA BCVA was found to be the single statistically significant predictor of BCVA gain following IVTA injection. In 8 patients (21.6%), the IOP increased above 25 mmHg postoperatively, and was successfully managed by medical treatment. Endophthalmitis did not develop in any of the patients. CONCLUSIONS IVTA injection produced a significant reduction of macular edema in eyes with BRVO either with or without prior grid laser treatment. Reduction of CMT increased the BCVA in most of the eyes receiving IVTA primarily, while only a slight improvement of BCVA was found in eyes with prior grid laser. The IVTA effect was transient. Larger studies are necessary to find the best approach (either grid laser or IVTA) to patients with macular edema associated with BRVO.