AbstractThe first requirement for adequate performance of an air turbine handpiece is sufficient power. Suppliers of such handpieces do not provide data on the power produced by their equipment. A method for determining the torque, speed and hence power during simulated operation is described. Forty‐one new and used handpieces were tested. Maximum speeds up to 500 000 rpm, maximum torques up to 2.33 N.mm and maximum power up to 29.6 watt were observed. The maximum power was produced at between 49 and 79 per cent of the free‐running speed. A relationship between maximum power and stall torque was noted. The maximum torque is at stall for ball‐bearing units. The stall torque can be easily determined by a simple stall torque test which is described. Using this test, the performance of handpieces can be easily checked in the clinic. The one air‐bearing handpiece tested performed in a manner similar to the others, except that stall occurred below 60