Versican is a modular proteoglycan harboring a hyaluronan-binding domain at its amino-terminal end and a selectin-like domain at its carboxyl-terminal end, separated by a large intervening region containing the attachment sites for the glycosaminoglycan side chains. By virtue of its modular nature, versican may play a role in cellular attachment, migration, and proliferation by interacting with cell surfaces and extracellular matrix molecules. To discern the function of versican through the analysis of spontaneous and targeted genetic mutations, we have isolated a mouse versican cDNA encoding part of the hyaluronan-binding region, analyzed its mRNA expression in various adult mouse tissues and embryos, and determined the chromosomal location of the gene. Murine versican was 89% identical to human versican at the amino acid level and was highly expressed in mouse embryos at Days 13, 14, and 18. Expression was also detected in adult mouse brain, heart, lung, spleen, skeletal muscle, skin, tail, kidney, and testis. Using interspecific backcross analysis, we assigned the versican gene (Cspg2) to mouse chromosome 13, in a region that is syntenic with the long arm of human chromosome 5 where the human CSPG2 gene is located.