Aims A randomized trial was performed to assess the safety and efficacy of a laser guidewire, in the treatment of chronic coronary occlusions. Methods and Results In 18 European centres, 303 patients with a chronic coronary occlusion were randomized to treatment with either the laser guidewire (n=144) or conventional guidewires (mechanical guidewire, n=159). The primary end-point of the study was treatment success, defined as reaching the true lumen distal to the occlusion by the allocated wire within 30min of fluoroscopic time: laser guidewire vs mechanical guidewire; 52·8% (n=76) vs 47·2% (n=75), P=0·33. Serious adverse events following the initial guidewire attempt were 0% (laser guidewire) and 0·6% (mechanical guidewire), respectively. Angioplasty (performed following successful guidewire crossing) was successful in 179 patients (91%, laser guidewire n=79, mechanical guidewire n=100), followed by stent implantation in 149 (79%). At the 6-month angiographic follow-up, the difference in binary restenosis rate (laser guidewire vs mechanical guidewire; 45·5% vs 38·3 %, P=0·72) or reocclusion rate (25·8% vs 16·1%, P=0·15) did not reach statistical significance. At 1, 6 and 12 months, angina and event-free survival were 69%, 35% and 24% (laser guidewire) vs 74%, 40% and 31% (mechanical guidewire). Conclusion Although laser guidewire technology was safe, the increase in crossing success did not reach statistical significance.