This paper reviews the literature on PTFE, PVC and stainless steel well casings and samplers and develops a series of suggested guidelines for use of these materials in sampling programs. Three factors are considered: the resistance of these materials to chemical reaction and thus degradation by the environment, the effect these materials have on the integrity of ground water samples, and the physical strength of these materials. Specifically, factors involved in the corrosion of stainless steel and the ability of aqueous solutions of organics to degrade PVC are discussed. Also considered are sorption and leaching of organic and metal species by these materials. The differences in the behavior of flexible vs. rigid PVC are emphasized.