Cholangioscopy and pancreatoscopy have been limited by current endoscopic technology. “Mother-baby” endoscope combinations use expensive and fragile “baby” scopes with limited longevity. Traditional baby scopes utilize imaging bundles that are limited in image quality (resolution, contrast, and color saturation). We have developed a new type of ultrathin, flexible endoscope or catheterscope that does not tradeoff a reduction in image quality with a reduction in scope diameter. The current forward-viewing prototype images at 500 lines resolution in a highly flexible 1.6 mm diameter shaft with a 13-mm long rigid tip. Full-color images are acquired at 15 Hz and with 80 degrees field of view in air or liquid. A prototype has been developed for ERCP. The prototype catheter scope was tested using a therapeutic duodenoscope in a synthetic human model (LM-014, Koken Co., Tokyo, Japan). The prototype was easily inserted into the pancreatic duct using direct visualization. This catheterscope is an example of a new technology platform for endoscopy. The core technology is a micro-optical scanner, less than 1 mm in diameter and less than 13 mm in length when sealed behind an objective lens system. The scanner is a singlemode optical fiber that is vibrated at its mechanical resonance by a 0.4 mm diameter piezoelectric tube. High-contrast color images are acquired by scanning red, green, and blue laser light in a spiral scan pattern (>200,000 pixels). The backscattered light is collected by a ring of 12 plastic optical fibers (0.25 mm diameter, Edmund Optics, Barrington, NJ) and detected by photomultiplier tubes in the portable base station. Low light levels are used for imaging, 2 mW per wavelength, which is equivalent to a laser pointer. A 1.6 mm diameter polyethylene sheath allows highly flexible bending of the shaft (6-mm minimum bend radius). The scanning fiber technology is versatile for many future endoscopic applications. Magnification endoscopy is possible by electronically reducing the scanning amplitude while acquiring 500-line images. Software can increase or decrease image resolution (to the optical limit) with a tradeoff in image frame rate. During insertion and navigation, the imaging can occur at higher frame rates (30 Hz) to minimize any motion distortion. During endoscopic examination, imaging can be at higher resolution (1000 lines per image). Fluorescence and narrow-band imaging are possible by adding appropriate laser excitation sources and additional filters and detectors in the base station. The authors acknowledge support for development of the catheterscope from the PENTAX Corporation and NIH/NCI CA094303.