The advanced development of the clinical everting (toposcopic) catheter is described. A detailed discussion of the design and outline of the fabrication techniques are followed by a thorough performance evaluation and summary of the first two clinical applications. The everting element is a low-durometer thermoplastic polyurethane elastomer. Surface treatments include the bonding of a hydrophilic polymeric coating, optimized for lubricity, to the sliding internal surfaces of the catheter. Eversion pressures and infusion/aspiration flow rates have been measured under various conditions and the infusate-in-blood mixing potential investigated. A preliminary assessment is given of the clinical performance of the catheter in the vascular delivery of chemotherapy and standard endoscopic retrograde cholangiopancreatography.