Abstract: The effective reach of a chain saw is increased by drive transmitting extension structure which is interposed between the cutting head and motor and handle unit. A first gearbox is attached against a side of the motor and handle unit and contains a pair of orthogonally positioned engaged bevel gears one of which is driven by the drive output element of the motor. A drive shaft extends forward from the first gearbox within a tubular extension arm to a second gearbox to which the cutting head is secured and which transmits drive to the cutting chain drive sprocket. The extension maintains the center of mass close to the operator to minimize strain on the operator and is largely free of exposed moving parts and structural convolutions that could entangle foliage during tree trimming operations or the like.