Objectives: Clinical assessment of diabetic macular edema before and after intravitreal triamcinolone acetonide injection, to determine the effectiveness, complications and their preventions. Subjects and Methods: Prospective study, observation on a series of clinical cases of diabetic macular edema seen at Cho Ray Hospital from, June, 01, 2010 to May, 31, 201l. Results: There were 31 eligible patients in the study group, male: 17 (54.8 percent ), female: 14 (45.2 percent ). Age 50 to 70: 80.6 percent, average: 58.3 years old. Time from diagnosis of diabetes to the appearance of macular edema is as early as 8 years, longest: 22 years. Average of 13.7 years. Lowest HbA1c is 6.0 percent , highest 9.0 percent . Average: 7.3 percent . Visual acuity 1/10: 29.1 percent. Macular thickness from 290.0 um to 920.0 um, average 524.6 um. - After 1 month of treatment, vision starts improving, best at 3rd month. At 6th month, some patients have worsened visions and recurrent macular edema. - Complications are not seen in the study group. Conclusion: After 1 month of treatment with intravitreal triamcinolone acetonide injection, vision improved and the level of macular edema decreased, best after three months. Some patients had recurrent macular edema, as well as decreased vision after 5-6 months. Normal and sever complications such as infection, intraocular hemorrhage, uveitis, retinal detachment, cataract rarely occur.