Non-MHC loci have been shown to play an important role in the development and regulation of graft-vs-host disease (GVHD). In the murine model of GVHD under study, injection of C57BL/6 spleen cells into unirradiated (C57BL/6 x DBA/2)F1 hybrid recipient mice results in an acute form of GVHD characterized by CTL, suppressor cells, and runting. In contrast, injection of DBA/2 spleen cells into the same recipients results in a chronic form of GVHD that is characterized by a lack of CTL and hyperproduction of Ig and autoantibodies. After preliminary studies with the use of congenic mice showed that non-MHC loci were controlling GVHD responses in this model, genetic analysis of GVHD response of BXD recombinant inbred strains and (B10.D2 x DBA/2) X DBA/2 BC mice identified a single locus, Gvh, on chromosome 7 that controls whether acute or chronic GVHD results from injection of parental lymphocytes into unirradiated (C57BL/6 x DBA/2)F1 recipient mice.