Abstract: A surgical instrument for the treatment of stenotic and occlusive coronary artery disease is described whereby the lumen of the coronary artery is longitudinally incised sub-epicardially through an area of narrowing or obstruction immediately whereafter dilation of the arterial lumen at the site of the stenotic blockage and arterial incision is effected by expansion under pressure of a balloon passed to the site through the artery. This coronary artery cutting and dilating instrument has a flexible probe at the distal end for guidance through the coronary artery, followed, in succession, by one or more radially extending knife blades for making the coronary incision and an inflatable balloon for dilating the stenotic artery zone immediately after the incision. A flexible inflating and control tube extends from the balloon to the proximal end, whereat a surgical syringe is connectable to effect hydraulic inflation of the balloon.