THIS report, preliminary in nature, concerns itself with the effect of laser on the exposed surface of in vivo carcinoma in man. LASER is an acronym for Light Amplification by the Stimulated Emission of Radiation. It represents a technological advance in instrumentation by which atoms are stimulated to emit light in same phase and direction at a given frequency. This yields a unidirectional, coherent, intense, monochromatic beam of high energy content. When a solid-state system is used, a pulsed, high-peak power output is achieved which can be focused through a lens to an impact site, to produce a maximum in power density. Thus, the ruby laser used in this study was emitting light at a wave length of 6,943 Angstroms with the delivery of 1 to 3 joules of energy in a pulse duration of 0.0005 seconds. By calculation, this is a rated power output of 2,000 to 6,000 w.