Abstract: A medical or dental handpiece for the performance of laser radiation treatments, composed of: an elongate housing constructed to be held in the hand, the housing having a radiation delivery end and enclosing a chamber which is adjacent the radiation delivery end; a radiation conducting element disposed in the housing for conducting laser radiation from a laser source into the chamber and toward the radiation delivery end; and a gas flow path in the chamber for guiding a flow of cooling gas through the chamber in a direction from the radiation conducting element toward the radiation delivery end.