Recently, access to the coronary arteries became available to laser angioplasty based upon a new concept which utilizes a pulsed laser source and multifiber, `over-the-wire' guided catheters. The aim of this study was to evaluate the early and long-term results and the side effects of coronary angioplasty using an excimer or a Holmium:YAG laser. Forty consecutive patients were treated with the Holmium:YAG laser (group I) and 46 consecutive patients were treated with the excimer laser (group II). The primary laser angioplasty success rate was 55% and 71.7% for group I and II, respectively. It was similar in calcified and in non-calcified lesions and in total occlusions and stenoses. Laser stand-alone therapy was obtained in 5.0% of group I patients versus 21.7% in group II patients (p < 0.05). Failures were due to the inability for the laser catheter tip to reach the lesion, to cross the obstruction, or to obtain a significant reduction in stenosis. They were more frequent in group I than in group II patients (45% versus 28.3%). Complications included acute closure in 7.5% of group I and 17.1% of group II patients and spasm in 10.0% and 13.0% of group I and group II patients, respectively. Dissection occurred more frequently in group II than in group I patients (28.3% versus 7.5%, p < 0.04). The angiographic patency rate at 6 month follow up was 33% and 29% for group I and group II patients, respectively. Multifiber, wire-guided catheters provide an easy access to the coronary arteries. Excimer laser angioplasty using large, densely packed catheters is effective but induces a high rate of dissections. Technical improvements are required to ablate more tissue to possibly reduce the restenosis rate. Further studies ar needed to elucidate the mechanism of side effects to reduce their impact on restenosis rate.