AbstractThe focus of this protocol is mouse hepatitis virus (MHV), with occasional references to other coronaviruses. Many of these protocols can be easily adapted to other coronaviruses. Protocols for propagating MHV in DBT and 17CL‐1 cells; the storage and titration of viral stocks; purification of MHV on sucrose gradients; and the generation of recombinant viruses by a cDNA assembly method and by targeted recombination will be presented. Protocols are also included for the propagation of DBT, 17CL‐1, and L2 cells used for growing and titrating MHV, and for the growth of BHK‐R cells and FCWF cells. The latter two cell lines are used for regenerating infectious MHV by an in vitro cDNA assembly protocol and by a targeted recombination protocol, respectively, allowing reverse genetic manipulation of these viruses. An additional protocol for the maintenance of the large plasmids used for generating recombinant MHVs will also be presented. Curr. Protoc. Microbiol. 21:15E.1.1‐15E.1.46. © 2011 by John Wiley & Sons, Inc.