Abstract: A cam phaser is disclosed for adjusting the angular position of a camshaft relative to a crankshaft. In a first embodiment, a rotatable camshaft has an interior passageway and at least one cam operative to effect actuation of an engine valve. A first drive member is connectable to the crankshaft for rotational movement therewith. The first drive member is independently rotatably associated with the camshaft. A piston member is axially moveably disposed within the camshaft interior passageway and associated with the camshaft for rotation therewith. The piston member is further associated with the first drive member for rotation therewith and axial movement relative thereto. Axial movement of the piston member effects a change in the angular position of the first drive member. In a second embodiment, a rotatable tubular member has an interior passageway.