Laser angioplasty can now be performed on the coronary arteries as sources of pulsed laser and steerable multifibre catheters have become available. The aim of this study was to analyse the immediate results, the outcome and secondary effects of coronary angioplasty with excimer and holmium YAG laser. The homium-YAG laser was used in 40 patients (Group I) and the excimer laser in 46 patients (Group II). The immediate success rates were 55% in Group I and 71.7% in Group II. The highest success rates were obtained in lesions of saphenous vein grafts. The primary success rate was remarkably high in calcific lesions and complete occlusions. It was less impressive in long than in short stenoses in Group I. Treatment by laser coronary angioplasty alone was successful in 21.7% of patients in Group II and 5.0% of patients in Group I (p < 0.05). The failures were related to difficulty in reading the lesion, in passing the stenosis or in obtaining a reduction of its severity. The failures were more common in Group I (45%) than in Group II (28.3%). In this preliminary series there were no deaths, myocardial infarcts or emergency coronary bypass procedures. The following complications were observed: acute occlusions in 17.1% of patients in Group I and 7.5% of patients in Group II; spasm (10-13%); coronary dissection was commoner in Group II (28.3%) than in Group I (7.5%, p < 0.04). Angiographic and clinical follow-up at 6 months showed a restenosis rate of 46% in Group I and 43% in Group II.(ABSTRACT TRUNCATED AT 250 WORDS)