An electromechanical surgical system comprises a hand-held surgical instrument including an instrument housing defining a connecting portion for selectively connecting with a shaft assembly, the surgical instrument having at least one rotatable drive member, and an end effector configured to perform at least one function. The shaft assembly selectively interconnects the end effector and the surgical device. The shaft assembly includes a transmission housing and a force transmitting assembly for interconnecting the rotatable drive member and a rotation receiving member supported in the end effector.