Preliminary experiments on the induction of 1ocalized myocardial tissuie modification by microwave energy, without causing any cardiac arrhythmias, were the first step in the development of both microwave ablation and an innovative procedure called microwave balloon angioplasty (MBA). MBA combines the traditional angioplasty technique with microwave energy to open narrowed arteries and reduce the occurence of restenosis. Microwave balloon angioplasty was used in anesthetized rabbits to induce tissue modification in the intima, media and adventitia. Resu1ts of initial in-vitro and in-vivo experiments are presented, and the potential advantages of adding microwave heating to balloon angioplasty are discussed.