Abstract: A variable displacement hydraulic motor/pump apparatus 10 of the axial piston type is described that is more efficient over a wider range of speeds than previous devices. The apparatus 10 includes a main shaft 17 having a piston rod carrier 30 extending radially outward from the shaft for supporting a plurality of radially and angularly spaced piston rods 37. The piston rods 37 are double ended and held axially stationary with respect to the main shaft. Pistons 51 and 52 are mounted at the ends of the piston rods 37. Annular cylindrical barrels 60, 61 are supported by barrel carrier assemblies 84, 85 respectively circumferentially about the main shaft. Torque is transmitted between annular cylinder barrels 60, 61 and the main shaft 17 by the carrier 30. The barrels have piston cavities 65 formed therein for receiving corresponding pistons 51, 52.