To establish the optimal conditions for recanalisation of obstructed arteries without damage to vessel walls, a Nd-YAG laser coupled to a 0.2 mm diameter optic fibre was used on obstructed human cadaver coronary and peripheral arteries and on popliteal arteries in amputated limbs. Vaporization of atheromatous plaques was consistently obtained with an energy of 360-600 J and a diluted blood perfusate (3 g/100 ml haemoglobin) at a rate of 20 ml/min. The arterial wall was protected from thermal injury by inserting the optic fibre into an inflated balloon catheter and by cooling the system with the perfusate. Since recanalisation of occluded arteries was consistently obtained without damage to the arterial wall or debris and thin and flexible optic fibres were easy to guide in the arteries, percutaneous transluminal Nd-YAG laser angioplasty was used in obstructed femoral and popliteal arteries in three patients. The first European trials in man showed the method to be feasible, effective, and harmless, although further studies are required to improve penetration of the obstruction and increase the diameter of tunnel.