A surgical instrument 4 is a coaxial arrangement of an inner shaft 14 and an outer sleeve 12 with grasping forceps or a cutting tool at the distal end 6. The proximal end of the instrument can be attached to an operating handle 2 by one of two locking mechanisms. In the first, a relief 24 is cut into the proximal end of the inner shaft and can be engaged by translation of a keyhole shaped element (38, figure 3) in the handle in the plane perpendicular to the axis of the instrument. In the second, a hole is bored through the outer tube and receives a pin (46, figure 4) mounted in the handle. Preferably, the locking elements are biased by a spring into their locked positions and a release lever is used to permit attachment or removal of the instrument from the handle.
