The Monorail system (Schneider) consists of a balloon catheter in which the guidewire passes through the balloon itself, exits the catheter proximal to the balloon, and runs alongside its small shaft (3 French) through the length of the guiding catheter. It offers distinct advantages over conventional systems of coronary angioplasty. It facilitates contrast injections and permits rapid balloon exchanges. This system was used for coronary angioplasty in 273 unselected consecutive patients (age 59 +/- 10, mean 35 to 73 years). There were 216 patients (84%) undergoing single-vessel and 57 patients (16%) with multi-vessel coronary angioplasty. A total of 335 coronary stenoses were dilated, which included 35 total occlusions. The size of balloon used ranged from 2.0 to 4.25 mm (3.0 +/- 0.5 mm) and the severity of stenosis was 85 +/- 11%.