Endoscope for the minimally invasive examination or surgical treatment of a patient, comprising - a flexible tubular shaft for insertion into the patient, with a distal end, and - a grip for holding the endoscope, a distal end of the grip being attached to a proximal end of the shaft, - wherein the endoscope is provided with at least one working channel (50b, 50w, 50a) for internally guiding a surgical instrument and/or carrying water or air to or providing suction at the distal end of the shaft, - at least one groove (4, 4') extending substantially axially along the outer face of the shaft from the vicinity of the proximal end to the distal end, where the groove (4, 4') ends in a recess (41, 41') in the distal end, and - the at least one working channel (50b, 50w, 50a) is provided by at least one hollow tube (5, 5b, 5a, 5w) that is removably housed in the groove (4, 4'), and - wherein a convex hull or a completion of the shaft to a simple geometric shape without the hollow tube (5, 5b, 5a, 5w) is the same as a convex hull or completion of the shaft with the hollow tube (5, 5b, 5a, 5w), characterized in that for better adaptation to length changes of the groove as a result of bending the shaft the tube (5, 5b, 5a, 5w) has at least one free section in which the groove (4, 4') and the tube (5, 5b, 5a, 5w) are dimensioned relative to one another in such a way that the tube (5, 5b, 5a, 5w) has play in the axial direction, but also in respect of a rotation of the tube around its local longitudinal axis, by way of the tube having, in the straight extended state of the shaft, an exterior cross-section which is slightly smaller than an interior cross-section of the groove (4,4'), and in that beyond and/or between the free section or free sections respectively are sections of the tube (5, 5b, 5a, 5w) which are inserted more firmly into the groove (4,4'), in that they are either pressed in exploiting the elasticity of the tube, or, alternatively or additionally, glued in with a not very strong adhesive. - a flexible tubular shaft for insertion into the patient, with a distal end, and - a grip for holding the endoscope, a distal end of the grip being attached to a proximal end of the shaft, - wherein the endoscope is provided with at least one working channel (50b, 50w, 50a) for internally guiding a surgical instrument and/or carrying water or air to or providing suction at the distal end of the shaft, - at least one groove (4, 4') extending substantially axially along the outer face of the shaft from the vicinity of the proximal end to the distal end, where the groove (4, 4') ends in a recess (41, 41') in the distal end, and - the at least one working channel (50b, 50w, 50a) is provided by at least one hollow tube (5, 5b, 5a, 5w) that is removably housed in the groove (4, 4'), and - wherein a convex hull or a completion of the shaft to a simple geometric shape without the hollow tube (5, 5b, 5a, 5w) is the same as a convex hull or completion of the shaft with the hollow tube (5, 5b, 5a, 5w), in that for better adaptation to length changes of the groove as a result of bending the shaft the tube (5, 5b, 5a, 5w) has at least one free section in which the groove (4, 4') and the tube (5, 5b, 5a, 5w) are dimensioned relative to one another in such a way that the tube (5, 5b, 5a, 5w) has play in the axial direction, but also in respect of a rotation of the tube around its local longitudinal axis, by way of the tube having, in the straight extended state of the shaft, an exterior cross-section which is slightly smaller than an interior cross-section of the groove (4,4'), and in that beyond and/or between the free section or free sections respectively are sections of the tube (5, 5b, 5a, 5w) which are inserted more firmly into the groove (4,4'), in that they are either pressed in exploiting the elasticity of the tube, or, alternatively or additionally, glued in with a not very strong adhesive.