This unit provides procedures to design, create, and utilize polycistronic plasmids that express multicomponent protein complexes in E. coli. Both the original pST39 polycistronic expression system, which permits four genes to be coexpressed from a single plasmid, and the more recent pST44 polycistronic system, which facilitates incorporation of affinity tags and simplifies the construction of variant deletion or point mutation polycistronic plasmids, are described. Emphasis is placed on practical details for creating polycistronic expression plasmids, expressing the protein complex in E. coli, purifying the protein complex, and troubleshooting potential expression problems. (c) 2008 by John Wiley & Sons, Inc.