AIMS: To evaluate the clinical outcome after treatment of coronary in-stent restenosis. METHODS AND RESULTS: For identification of the relevant literature a specific search strategy was conducted and explicit inclusion criteria were defined to avoid selection bias. Based on the selected literature, a systematic review using descriptive statistics and meta-analysis methods regarding the outcome after treatment of coronary in-stent restenosis was performed. The proportion of patients experiencing a major adverse cardiac event (MACE) as defined by death, myocardial infarction, and target lesion revascularization was the main outcome measure. A total of 1304 citations were identified. Among these, 28 studies (six different treatment modalities) including a total of 3012 patients met the inclusion criteria and were incorporated into this analysis. The estimated average probability of experiencing a major cardiac adverse event after treatment for in-stent restenosis with a follow-up period of 9+/-4 months was 30.0% (25.0-34.9%, 95% confidence interval) with strong evidence for heterogeneity between study specific results (P=0.0001). The clinical outcome was not significantly different between treatment modalities. After adjustment for confounding factors (i.e. lesion length), however, patients undergoing intracoronary radiation showed an estimated advantage of 16.9% (-37.7+/-4.0%, 95% confidence interval) in MACE free survival, as compared to balloon angioplasty. The post-interventional diameter stenosis was the only independent predictor for the long-term outcome after treatment of in-stent restenosis. CONCLUSIONS: Treatment of in-stent restenosis is associated with an overall 30% rate of major adverse cardiac events. Currently, repeat angioplasty is the treatment option of choice, especially when a sufficient acute procedural result can be achieved. Intracoronary radiation should be considered in cases with therapy refractory forms of diffuse in-stent restenosis.