Porcine enteric calicivirus (PEC) is a member of the genus Sapovirus in the family Caliciviridae. This virus causes diarrheal illness in pigs, and is presently the only enteric calicivirus that can be grown in cell culture. In addition to its relevance to veterinary medicine as a diarrheal agent in pigs, PEC serves as an important model for the study of enteric caliciviruses that cause diarrhea and that cannot be grown in cell culture (including the noroviruses represented by Norwalk virus). The development of an infectious cDNA clone is important because it enables the use of “reverse genetics” to engineer mutations of interest into the genome of PEC and to study their effects. In addition, it allows the introduction of foreign coding sequences into the genome of PEC that could be useful for vaccine development in swine and possibly humans. This discovery has both basic research applications such as mapping mutations involved in tissue culture adaptation, tissue tropism, and virulence as well as practical applications such as providing a genetic backbone for the development of chimeric vaccine viruses.