A laser ablation catheter system guided by ultrasound sonography particularly useful for removing atherosclerotic plaque from coronary arteries of patients with heart disease and it method of use are detailed. Ultrasound is employed at the tip of the catheter to determine where the plaque is with reference to the arterial wall. After a sonographic image is made, an ablative laser element is aimed at the plaque to ablatively remove the plaque under computer guidance. In one embodiment, the laser is able to fire in a forward direction after first determining the laser's path to be intralumnal in order to create or recanalize a central channel. In another embodiment, the laser is able to fire circumferentially at the arterial wall guided as to depth and direction by the ultrasound computer interface. Both functions may be provided in one laser angioplasty catheter system. The system also includes manual and computer safety overrides. A proximal occlusion balloon normally will be used to provide stabilization of the catheter and a blood-free environment.