A control system for a laser catheter device wherein the control system is provided with means for determining the intensity of laser beam energy at two points, one of which is at the distal tip end thereof, and with the other being interposed along a transmitting column remote from both the source of laser beam energy and the distal tip. A beam splitter means(dichroic filter) is provided for diverting a first portion of the laser beam energy onto a first detector means. Energy passing through the beam splitter is ultimately directed onto a fluorescent member or device disposed adjacent the distal tip, with the fluorescent member or means being capable of emitting or generating radiant energy at a wavelength significantly different from that of the incident laser beam energy. The radiant energy generated by the fluorescent means is directed onto a second surface of the beam splitter means, and ultimately onto a second detector means. First and second signal processing means responsive to the first and second detector means are utilized to control a shutter, such as a dual shutter, which is arranged to interrupt the passage of laser beam energy through the catheter system upon the occurrence of anomalous levels of laser beam energy at either the first or second detector means.