A guiding catheter system uses one or more steering lumens embedded within the walls of a flexible shaft. The steering lumens are in fluid contact with inflation lumens that are accessible from a proximal part of the guide catheter. The catheter is steered by pressurizing or depressurizing the inflation lumens, thereby inflating or deflating the steering lumens. The change in steering lumen pressure causes a change of the catheter's distal end, allowing the catheter to be steered.