Abstract: Motor drive unit for use with an atherectomy device having a flexible drive cable and a finger operated member for advancing and retracting the drive cable. The drive unit comprises a motor and a power supply mounted in a case of a size which fits comfortably in a human hand, with a power switch positioned for operation by a finger of the hand holding the case. When the motor is connected to the drive cable, the finger operated member can be operated by a finger of the hand holding the case to advance and retract the cable and the cutter connected thereto.