A hemostasis valve assembly adapted for use within a catheter introducer is disclosed. The valve assembly includes first, second and third sealing members wherein the second sealing member comprises a guide wire seal. The guide wire seal includes a plurality of lip members defining two pairs of diametrically opposed slits and an aperture intersecting at least one of the slits. The aperture is adapted to sealing engage a small diameter guide wire for preventing fluid flow out of the catheter introducer through the valve assembly, while the slits allow for the passage of a large diameter elongated member or catheter. Two pairs of diametrically opposed pre-load ribs extend radially towards the aperture for pressing the lip members together in sealing engagement. A substantially spherical inner surface is provided for guiding the guide wire to the aperture.