An endoscopic or laparoscopic surgical instrument having an internally disposed locking mechanism located within a barrel portion of a handle assembly. The instrument includes a handle assembly having a pivoting handle and a stationary handle, a barrel portion to which an elongated body assembly is secured, and a locking mechanism for releasably positioning a tool mechanism located at the distal end of the body assembly. In one embodiment the locking mechanism comprises a trigger, a brake and a latch spring. In another embodiment the locking mechanism comprises a latch spring and a locking block. A rotational knob and locking member may also be provided to position the body assembly at various orientations to the longitudinal axis.