A dilation balloon is provided for an intravascular catheter having an elongated shaft with a proximal portion, a distal portion, and an inflation lumen extending therethrough. In one aspect of the invention, the dilation balloon includes a balloon member having a chamber therein in fluid communication with the inflation lumen. The balloon member defines a portion of a guide wire lumen which coextends with a portion of the balloon member for receiving a guide wire. In another aspect of the invention, a balloon is connected to the distal portion of the catheter shaft and a guide wire lumen is spaced exteriorly from the shaft and coextends with a portion of the balloon. In yet another aspect of the invention, a process for making a dilation balloon includes the step of providing a longitudinal member having a first elongated lumen and a second elongated lumen. A first portion of the longitudinal member which defines the first lumen is blow molded into an inflatable balloon which defines an interior chamber for receiving inflation fluid. A second portion of the longitudinal member which defines the second lumen is blow molded into a longitudinal rib which defines a guide wire lumen coextending with said chamber.