A sealing arrangement for a medical introducer having a distal end for introduction into a patients blood vessel. The introducer includes a flexible sealing member having an aperture for introduction of a guide wire or other medical device therethrough. A constraining structure, such as a washer, tightly contacts and surrounds the sealing member just proximal to an enlarged diameter flange at the distal end of the sealing member. The inner diameter of the constraining member is less than the outer diameter of the flange providing a constraint on the sealing member and lessening the distortion of the sealing member normally occasioned when a device is pulled outwardly or proximally through the introducer away from the patient. When the constraining structure is a washer, the washer is easily assembled to the introducer by simply being fitted into an annular notch formed just proximal to the distal end of the sealing member.
