A beam of infrared energy from a CO.sub.2 laser operating in its lowest order spatial mode is passed through a converging lens and directed to an operating site by a mirror or beam splitter. In order to locate the invisible focused spot of infrared energy a beam of visible light from a He-Ne laser is introduced coaxially into the path of the CO.sub.2 laser beam by a removable mirror. In another embodiment the He-Ne beam is passed through a beam splitter to form two parallel channels focused by microscope objectives on the input ends of respective fiber optic light guides. A rotating chopper disc is positioned in front of the light guides to alternately block and pass light in each channel. The other ends of the light guides are connected to marker projectors located above the beam splitter for the CO.sub.2 beam, but just out of the field of view of an overhead operating microscope. A lens and mirror system in each projector focuses the visible light through the beam splitter onto the focal point of the CO.sub.2 beam at the operating site. If the intended site is above or below the CO.sub.2 beam focal point, spaced red dots alternating at the frequency of the chopper disc will appear to the viewer through the microscope, indicating the need for further adjustment. Perfect adjustment is indicated by a single non-flashing dot.