We have constructed a physical map of a >2-Mb region on mouse chromosome 6 that contains the natural killer gene complex (NKC). The map comprises a contig of 14 overlapping yeast artificial chromosomes onto which we positioned 25 NKC markers. NKC genetically linked genes encode >17 proteins that directly control innate NK cell-mediated tumor lysis and disease resistance. Herein we show that Nkrp1 genes are clustered in a region flanked by A2m and Cd69 genes and that most Ly49 genes are clustered in a distal region ~1 Mb distant. Importantly, syntenic intervals of mouse chromosome 6 and human chromosome 12p that include the NKC are conserved. NKC species conservation suggests that the human NKC may contain orthologues for the mouse viral disease resistance genes, Cmv1 and Rmp1. The high-resolution NKC map will facilitate investigation of NKC gene regulation and identification of phenotypically defined gene products that confer NK cell defense against viral pathogens.