Despite widespread use of coronary balloon angioplasty, advances in angioplasty technology, and improvements in operator technique, restenosis at the angioplasty site is the major problem limiting the long-term efficacy of this procedure. The article reviews morphologic-histologic observations at angioplasty restenosis sites, speculates about the connection between the acute injury patterns of balloon angioplasty and the development of restenosis, and briefly reviews the currently understood pathways to restenosis and possible approaches to its reduction or elimination.