In vitro studies demonstrate that porcine relaxin may possess various therapeutic effects. In this study, we explore the possibility of expressing porcine relaxin in transgenic tobacco. Tobacco was selected because it is a non-food, non-feed crop, and recombinant protein production can readily be scaled up. The cDNA of porcine preprorelaxin was under the regulation of two different constitutive promoters. DNA analysis by polymerase chain reaction verified that all transgenic plants contained the correct size of gene insert. Preliminary studies showed the presence of putative prorelaxin bands in both silver-stained SDS-PAGE and western blot. The results also indicated that tobacco-produced prorelaxin may not be properly processed to yield the mature relaxin.