Background and Objective: Holmium:YAG is a solid-state, investigational coronary laser device. Preliminary reports indicate the clinical potential for this laser; however, its safety and efficacy in a single center experience have not yet been reported and analyzed in detail. Study Design, Patients, and Methods: One hundred and twelve consecutive symptomatic patients underwent percutaneous holmium:YAG laser (2.1 micron wavelength, 250-600 mJ/pulse, 5 Hz) facilitated coronary angioplasty. Sixty-six patients (Or 1) had 74 thrombotic lesions, and 46 patients (Gr 2) had 55 thrombus-free stenoses. Results: Overall laser success was achieved in 120 out of 129 lesions (93%), with 95% subsequent balloon angioplasty success. Laser and clinical successes among the two groups were similar. By quantitative coronary angiography, reduction in the percent diameter stenosis (mean +/- SD) was similar (79 +/- 16% to 37 +/- 14% vs. 73 +/- 16% to 37 +/- 11.5%; P = NS) in both groups. However; minimal luminal diameter improved significantly more in Or 1 patients, (0.7 +/- 0.5 mm to 2.0 +/- 0.5 mm, vs. 0.9 +/- 0.4 mm to 1.8 +/- 0.4 mm, P = 0.03). Angiographic and clinical complications were similar in patients with thrombus and without thrombus. No death, perforation, or Q-wave infarction occurred in the catheterization laboratory in either group. In-hospital mortality occurred in two patients from cardiac causes unrelated to the laser application. Of the 98 patients who reached the 6 month anniversary, 76 (77%) remained asymptomatic. The restenosis rate among the patients who underwent repeat angiography was 50%. Conclusions: Solid-state, mid-infrared laser can be safely and successfully applied to symptomatic patients with thrombotic and nonthrombotic lesions, Similar to other debulking devices, the effectiveness of this laser in yielding long-term patency has not been proved. (C) 1996 Wiley-Liss, Inc.