THE RECENT development of flexible fiber-optic lighting and optical viewing systems has made possible visualization of previously inaccessible areas. The clinical practicality of the flexible choledochoscope described by Shore and Lippman1 has led to an investigation of the value of this instrument for operative visualization of the interior of major arteries. The flexible choledochoscope is 50 cm in length and 7 mm in diameter, with the optical, lighting, and irrigating systems housed within a single latex and vinyl copolymer sheath (Fig 1). The light source is a fiber-optic power supply unit to which is attached a 6-foot long, ¼-inch diameter fiber-optic cord. This provides a maximum of 660 foot-candles of light at a distance of 1 cm from the objective lens with no transmission of heat. The forward-viewing objective lens has an angle of view of 40° with great depth of field and can produce a clear image even