AbstractSince laser energy has been shown to produce controlled thermal injury to atherosclerotic plaques from postmortem human hearts, a 3‐mm diameter fiberoptic catheter was devised and tested for use in peripheral vessels. The catheter has channels for viewing, laser delivery, and suction/flushing. In five femoral or carotid arteries from three dogs implanted with near‐total human atherosclerotic obstructions, the fiberoptic catheter was capable of viewing and targeting the atherosclerotic plaque for laser irradiation. The plaque was vaporized using 5 watts with time exposures lasting from 2 to 5 sec from an argon‐ion laser. In three other animals each implanted with a 3‐ to 4‐cm long segment of human cadaver atherosclerotic vessel, the fiberoptic catheter clearly visualized the internal diseased vascular wall. Thus, this investigation provides the initial demonstration and practicality of applying a flexible dual fiberoptic catheter for simultaneous in vivo visualization and laser vaporization of peripheral atheroscleroti