A laser microsurgical method and apparatus are disclosed for safely treating occluded body lumens with laser energy. The disclosed method involves the use of pulsed laser energy from an argon-ion laser to destroy the tissue of luminal occlusions, such as atheromatous plaque and the like, with substantially no thermal necrosis of the surrounding tissue. A flexible catheter and associated laser microsurgical system is also disclosed which provides for aiming of the fibers to transmit the laser beam at the distal end of the catheter and rotational positioning of the catheter to permit coverage of virtually the entire cross-sectional area of the lumen. A lens system at the distal end of each laser fiber minimizes beam divergence and directs the beam toward the central axis of the catheter. A further embodiment of the catheter of the invention provides an array of laser fibers which are optically scanned with laser energy to cover the cross-sectional area of the lumen. The system is designed to minimize the possibility of damage to or perforation of the surrounding tissue of the lumen.