In therapeutic flexible endoscopy a team of physician and assistant(s) is required to control all independent translations and rotations of the flexible endoscope and its instruments. As a consequence the physician lacks valuable force feedback information on tissue interaction, communication errors easily occur, and procedures are not cost-effective. Current tools are not suitable for performing therapeutic procedures in an intuitive and user-friendly way by one person. A shift from more invasive surgical procedures that require external incisions to endoluminal procedures that use the natural body openings could be expected if enabling techniques were available. This paper describes the design and evaluation of a robotic system which interacts with traditional flexible endoscopes to perform therapeutic procedures that require advanced maneuverability. The physician uses one multi-degree-of-freedom input device to control camera steering as well as shaft manipulation of the motorized flexible endoscope, while the other hand is able to manipulate instruments. We identified critical use aspects that need to be addressed in the robotic setup. A proof-of-principle setup was built and evaluated to judge the usability of our system. Results show that robotic endoscope control increases efficiency and satisfaction. Participants valued its intuitiveness, its accuracy, the feeling of being in control, and its single-person setup. Future work will concentrate on the design of a system that is fully functional and takes safety, cleanability, and easy positioning close to the patient into account.