A balloon catheter comprises a catheter and a balloon located on the distal end of the catheter. A pair of stimulating electrodes for receiving a constant current stimulating signal when the balloon is inflated with an electrically conductive medium and a plurality of sensing electrodes for producing voltage response signals are located on the catheter. The voltage response signals are indicative of the values of the transverse cross-sectional area of the balloon adjacent the sensing electrodes. A first lumen accommodates the inflating medium to and from the balloon, and a second lumen accommodates electrically conductive wires to the stimulating and sensing electrodes. A pressure sensing element is located in a protective housing in the second lumen, and communicates through a communicating opening in the protective housing and through a communicating port in the catheter with a hollow interior region of the balloon. The balloon catheter may also be provided with a guide wire engaging element for engaging a guide wire externally of the balloon catheter.