Volatile organic compounds pose a challenge to groundwater sampling protocols, since they can be lost as a water sample degasses or lost due to sorption on tubing or pump materials. Laboratory sorption experiments have been conducted with five common flexible tubing materials to determine the impact of sorptive bias for chloroform, trichloroethylene, trichloroethane, and tetrachloroethylene. Tubes made of Teflon, polyethylene, polypropylene poly(vinyl chloride), and silicone rubber were all found to sorb the test compounds in short exposure periods. Virgin tubing materials introduce substantial amounts of leachable organic matter in similar exposures. Tubing made of Teflon showed the least absorption and leaching problems and should be the tubing material of choice for detailed organic sampling purposes. Absorption into the polymer matrix is the likely mechanism for the errors. (Copyright (c) 1985 American Chemical Society.)