A balloon catheter has a balloon membrane, a tip connected to the distal end of the balloon membrane and an outer tube connected to the proximal end of the balloon membrane for supplying a medium for inflating and deflating the balloon membrane. A pressure sensor, such as a fiber optic sensor, may be mounted in a pocket in the tip. The pocket may be filled with a flexible substance which both communicates pressure to and protects the pressure sensor. A membrane may overlie the pocket to prevent leakage of the flexible substance therefrom.