Abstract: A camshaft for an internal combustion engine having a hollow shaft carrying one or more cams or partial cams for rotation therewith and an inner shaft disposed within the hollow shaft and rotatable relative to the hollow shaft. The inner shaft has one or more cams or partial cams disposed outside the hollow shaft attached for rotation with the inner shaft through clearances in the hollow shaft. A camshaft drive includes a means responsive to the parameter characteristic of engine operating conditions for adjusting the rotational position of at least one of the shafts relative to the drive. The adjustment mechanism includes a radially extending guide on the drive, and an adjustment cam having a cam surface thereon and mounted on the guide to be radially displaceable therealong. A means is provided responsive to the desired engine parameter for varying the radial displacement of the adjustment cam.