Chronic wasting disease (CWD) of deer and elk and sheep scrapie are transmissible spongiform encephalopathies, or prion diseases, and are maintained in animal populations by animal-to-animal transmission. In both diseases, strong circumstantial evidence suggests an environmental reservoir may be involved in the transmission of the putative infectious agent, an abnormally folded form of the normal prion protein. Both insect vectors and soil have been proposed as possible reservoirs of infectivity. Current knowledge on the role of these reservoirs in the transmission of prion diseases will be discussed.