CO₂, contact Nd : YAG and Combolaser (combined, simultaneous and coaxial CO₂ + Nd : YAG laser beam) were used for uvulopalatopharyngoplasty (UPPP). It has been proposed that the combined beam geometry diminishes thermal damage to surrounding tissues when compared with single laser radiation. To study the extent of thermal tissue damage produced by the lasers, tissue samples for light (LM) and transmission electron microscopy (TEM) were taken from the surface of the resected area and 2 and 4 mm below the resection plane. The depth of tissue damage and coagulation was measured. The results showed no consistent differences in the inflammatory reactions or the amount and depth of tissue coagulation observed in samples taken immediately after the operation. The CO₂ laser typically produced a carbonized and coagulated wound edge. Combolaser and contact Nd : YAG lasers generated slightly less charring but otherwise resembled each other with coagulated and vacuolized resecate margins. These results indicate that the beam geometry in Combolaser does not diminish thermal damage to surrounding tissues.