A sheath catheter includes a positioning wire fixedly attached at its distal end to a distal tube. A proximal tube is slidably disposed on the positioning wire proximal of the distal tube and sized so that the distal tube may be nested therein. In one embodiment, a series of coordinating stops are fixed on the tubes so that the distal tube can slide back and forth within the proximal tube but cannot be extracted from the proximal tube. As such, the over-the-wire length of the catheter can be varied. In another embodiment, an additional telescoping portion can be added between the distal tube and the proximal tube for greater control over the length of the sheath catheter. In this embodiment, the tubes are sized so that the middle tube may be nested within the proximal tube and the distal tube may be nested in the middle tube.