Abstract: A mobile self-propelled aerial lift machine comprises a chassis, a swingable boom support structure mounted on the chassis, an elevatable telescopic boom mounted on the support structure and an adjustable work platform supported at the outer end of the boom. A plurality of hydraulic motors operable at variable speeds are provided to effect movement of the chassis, support structure, boom and work platform. The control system for the hydraulic motors includes an engine-driven destrokable radial piston-type pump mounted on the support structure and having a pressure port and a control (destroke) port whereby a change in the rate of fluid flow to the control (destroke) port effects a change in the fluid pressure at the pressure port. A plurality of solenoid operated selector valves are located on the support structure and are operable to permit fluid flow from the pressure port to the hydraulic motors.