This thesis examines the mechanisms of acute lumen enlargement after rotational atherectomy (RA) in case of an in-stent restenosis (ISR) and it assesses the results of adjunct balloon angioplasty (BA) and describes the predictors for a recurrent restenosis. ISR has become an important implication in interventional cardiology, mostly due to the increased rate of coronary stents being implemented. Next to the tissue debulking techniques, intra-coronary brachytherapy and the usage of drug-eluting stents show a promising reduction of these iatrogen lesions recently. Methods: RA with adjunct angioplasty was used in 40 patients (age 58±11) with diffuse ISR six month after initial stent implementation. Both a quantitative coronary angiographic (QCA) analysis and sequential intravascular ultrasound (IVUS) measurements were performed in all patients. 33 of these patients (89%) underwent an angiographic four-month follow-up. Results: The RA lead to a reduction in the maximal area of stenosis from 71±16% before the intervention to 35±13% after the RA (p<0.0001) as a result of a significant decrease in intimal hyperplasia (IH) cross-sectional area (CSA). The minimal lumen diameter after RA remained 8% smaller than the largest burr diameter used, indicating an immediate recoil of the neointima. An additionally performed BA led to a further decrease in the area of stenosis to 22±13% due to an expansion of the stent. The angiographic follow-up showed a recurrent restenosis rate of 45%, thus indicating the need for a target revascularization in 35% of all patients. Number and length of stents, the degree of the preinterventional diameter stenosis, and the amount of acute neointimal recoil were associated with a higher rate of recurrent restenosis. Conclusions: RA is a safe method and achieves an immediate increase of the lumen by effectively plaque removal in coronary stents. An adjunct BA, due to stent expansion, can accomplish an added lumen gain. The combined length of the stents, the degree of the preinterventional stenosis and the immediate neoimtimal recoil are predictors of recurrent restenosis. In the light of the newly developed techniques for reduction of a neointimal increase (brachytherapy, drug-eluting stents), debulking methods are used more and more less.