We looked at the results of 89 consecutive diabetic eyes with diffuse macular edema that had been treated with grid laser photocoagulation. Sixty (67%) eyes improved anatomically post-laser, ie the amount of edema was less. Fifteen (17%) eyes improved in visual acuity by two or more lines following treatment. Sixty-nine (77%) experienced no change, or changed by only one line; five eyes (6%) experienced a decrease in visual acuity by two or more lines. Clinical findings having significantly poorer visual prognoses were the presence of foveal exudate, hypertension, macular capillary nonperfusion, and poor preoperative visual acuity. Whether or not treated eyes do better than untreated eyes cannot be determined by a retrospective study such as this, and awaits the results of a larger, prospective, randomized, controlled, clinical trial.