A catheter introducer system for endoscopy is disclosed which includes a steering section and a propulsion section located near the end of the catheter that is introduced in a body cavity, and a non-collapsible sheath defining a working channel. The propulsion section is designed to pull the rest of the catheter inside the body cavity, so there is no need to push the catheter along. The propulsion section further includes gripping members, such as inflatable balloons, that are axially movable relative to the catheter. The catheter can thus be made very flexible in bending, and a larger diameter catheter can be used without discomfort to the patient.