Intravitreal ranibizumab (RBZ) has been shown in multiple randomized clinical trials to be a valuable treatment for diabetic macular edema (DME), promoting a significant improvement in best-corrected visual acuity (BCVA) and in anatomic outcomes. Compared to sham (RISE and RIDE studies), RBZ rapidly and sustainably improved BCVA and decreased macular edema at 2 years, reducing the risk of further vision loss, with low rates of local or systemic side effects. Compared to macular laser photocoagulation (READ-2 study), RBZ provided a greater improvement in BCVA and regression in foveal thickness, but required a higher number of injections compared to patients treated with both RBZ and laser. In RESTORE trial, RBZ alone or combined with macular laser turned out to be superior to laser alone, without significant differences between the 2 RBZ groups. Compared to combined treatment (RBZ or triamcinolone associated with macular laser) or photocoagulation laser alone (Diabetic Retinopathy Clinical Research Network trial), RBZ with prompt or deferred laser was more effective than laser alone at 1-year follow-up. At 3 years, prompt laser was not better than deferring laser for 24 weeks or more. At 5 years, subjects treated with RBZ achieved better long-term visual outcomes than patients managed with triamcinolone or laser followed by very deferred RBZ. In conclusion, randomized clinical trials showed that RBZ was superior to laser in DME treatment, providing excellent long-term visual outcomes. Frequent injections were necessary in most of the patients to properly control DME and maximize the visual benefits.