Abstract: An engine speed control system for a hydro-mechanical transmission of a vehicle including a mechanical transmission having a plurality of speed range change-over clutches and pairs of hydraulic pumps and motors, each motor being operatively connected to the mechanical transmission. The control system includes a throttle position detector for detecting throttling position of an engine and generating a throttle position signal. This signal is fed into an engine speed setter where target engine speeds corresponding to the throttle positions are stored. The engine speed setter then sends out a target engine speed signal. An engine speed detector is provided for detecting an actual engine speed and sending out an actual engine speed signal. This actual engine speed signal is compared with the target engine speed signal in a comparator and an engine speed difference signal is generated from the comparator.