Abstract: In the present apparatus, the removal of a dental handpiece from its holder opens a pilot-operated valve for supplying air or both air and water to the handpiece in conjunction with the usual foot pedal-operated valve.Preferably, the holder has aligned, narrow air passages on opposite sides of a recess which receives the handpiece, and the handpiece blocks these passages when it is in the holder. Upon removal of the handpiece, the flow of air from one of these passages across the recess and into the other passage supplies the pilot pressure for opening the pilot-operated valve. The pilot-operated valve may be separate from the holder or contained within it.In another embodiment, the holder has a reciprocable valve member controlling the application of pilot pressure to the pilot-operated valve. This valve member is depressed to a closed position by the handpiece when the latter is in the holder and is biased to an open position when the handpiece is removed from the holder.