Macroautophagy (herein autophagy) is a cellular process, requiring ATG5, by which cells deliver double membrane-bound packets containing cytoplasm or cytoplasmic organelles to the lysosome. This process has been reported in some cases to be antiviral, while in other cases it has been reported to be required for efficient viral replication or release. A role for autophagy in RNA virus replication has been an attractive hypothesis because of the association of RNA virus replication with complex membrane rearrangements in the cytoplasm that can generate opposed double membranes. In this study we demonstrate that ATG5 is not required for murine hepatitis virus (MHV) replication in either bone marrow derived macrophages (BMMฯ†) lacking ATG5 by virtue of Cre-recombinase mediated gene deletion or primary low passage murine ATG5-/- embryonic fibroblasts (pMEFs). We conclude that neither ATG5 nor an intact autophagic pathway are required for MHV replication or release. ยฉ2007 Landes Bioscience.