The temperatures elicited during drilling according to the osseointegration technique were measured in vivo in five edentulous human mandibles. The temperature changes were measured by a thermocouple, the tip of which was situated 0.5 mm from the drill surface and separated from it by a cortical wall. Eighteen measurements showed a mean initial temperature of 29.2 degrees C before drilling and a mean maximum temperature of 30.3 degrees C during drilling. The maximum temperature recorded was 33.8 degrees C. The duration of the maximum temperatures never exceeded 5 seconds. All temperatures recorded were below the level for impaired bone regeneration. It was concluded that drilling according to the osseointegration technique does not cause any impaired bone regeneration because of excessive heat production.