Abstract: An illuminator for a dental handpiece where the handpiece is of the type which has therein a light conductor that is small enough and light enough so that it can be mounted on and coupled directly to the handpiece. The light source in the illuminator is a quartz-halogen bulb. The illuminator housing provides for maintaining the quartz-halogen bulb at the necessary high temperature and in addition, provides for sufficient cooling and thermal insulation to protect the hand of the operator. The construction is such that a new bulb in its own housing can readily be substituted for the original on failure of the bulb.