Abstract: A variable speed shaft drive system for bicycles employs a drive shaft that is generally horizontally coupled between the pedals and the rear wheel of the bicycle. A pinion gear at the forward end of the drive shaft is engaged by a ring gear driven by the pedals to transmit drive power from the pedals to the drive shaft. A drive head at the rear end of the drive shaft frictionally engages a drive pick-up plate mounted to the rear wheel of the bicycle to transmit drive power from the rotating drive shaft to the rear wheel. Infinitely variable speed control is achieved by means of a shifting fork actuated by the user to position the drive head at selected distances from the center of the drive pick-up plate. Alternatively, a second drive head/pick-up ring combination may be substituted for the ring gear/pinion gear combination driven by the pedals to provide even smoother operation.