Abstract: A pneumatic power wrench which comprises a rotation motor (11) lodged in a housing (10) having air inlet and outlet passages (16, 23) for communicating air to and from the motor (11), respectively, and a power transmission for connecting the motor (11) to an output shaft (14), wherein the air outlet passage (23) comprises an adjustable air flow restricting mechanism (24) in the form of a valve spindle (29) extending substantially longitudinally through the outlet passage (23), an annular valve seat (34), and a valve element (32) supported on the valve spindle (29) for flow restricting cooperation with the valve seat (34). The valve spindle (29) is axially adjustable relative to the valve seat (34) for varying the flow restriction through the outlet flow restricting mechanism (24).