EcoRl, Hindlll, and Pstl restriction fragments representing the entire genome of the DN-599 isolate, the American prototype strain, of bovine herpesvirus 4 (BHV-4) were cloned. These cloned restriction fragments were analyzed by restriction enzyme digestion, hybridization to Southern blots of BHV-4 (DN-599) DNA, and cross-hybridization of cloned fragments. The resulting data were used to construct restriction maps of the unique region of BHV-4 (DN-599) DNA for restriction enzymes EcoRl, Hindlll, and Pistl. The EcoRl and Hindlll restriction maps confirm those previously deduced for the DN-599 isolate by hybridization of cloned fragments of a European strain of BHV-4 to Southern blots of DN-599 DNA. The Pstl restriction map is the first reported for BHV-4.