A detergent extract of 35S-methionine-labeled cytomegalovirus(CMV)-infected cells was analyzed by crossed-immunoelectrophoresis using human sera with high anti-CMV antibody titers. Six distinct precipitation lines could be seen in agarose gels after crossed-immunoelectrophoresis. On further analysis of the precipitation lines using SDS-PAGE, the proteins obtained could be related to proteins identical in size, obtained from purified CMV nucleocapsids.