Abstract: A shaft for a flexible endoscopic instrument is provided in which the shaft comprises a generally tubular frame member, the tubular frame member providing the shaft with at least one flexible section along the length of the shaft, the flexible section having a greater flexibility than at least one other section of the shaft. The flexible section of the shaft has a proximal end and a distal end, and is provided with first and second series of slots, the slots of the first series alternating with the slots of the second series to form an offset pattern of staggered slots in the frame member to provide the different stiffness properties. Each of the slots in a selected one of either the first or second series of slots is of a different length as compared to other slots in that series of slots, the slots in the selected series varying in length according to a predetermined progression, such that the flexible section is designed to deflect in a controlled and predetermined manner.