A combination guiding catheter assembly and a dilating catheter assembly. The guiding catheter assembly includes a first flexible tubular member formed of a material which has a low coefficient of friction and a second flexible tubular member encasing said first tubular member so that the first tubular member fits tightly in the second tubular member. The combined first and second tubular members have proximal and distal ends with a fitting mounted on the proximal end. The dilating catheter assembly includes a flexible tubular member. The tubular member of the dilating catheter assembly having proximal and distal ends and an inflatable annular portion formed integral with the tubular member of the dilating catheter assembly near the distal end thereof. A fitting is mounted on the proximal end of the tubular member of the dilating catheter assembly. The dilating catheter assembly is disposed within the guiding catheter assembly. An inflator is provided for inflating and deflating the inflatable annular portion.