The Vitek Immunodiagnostic Assay System (VIDAS; bioMerieux Vitek Inc., Hazelwood, Mo.) was evaluated for its ability to detect anticytomegalovirus immunoglobulin G (IgG) and was compared with the following assay systems: Abbott IMx Cytomegalovirus IgG antibody assay (Abbott Laboratories, Abbott Park, Ill.), Whittaker Cytomegelisa II IgG assay (Whittaker Bioproducts, Walkersville, Md.), and Whittaker FIAX Cytomegalovirus IgG assay (Whittaker Bioproducts). Samples were considered positive if at least two of three (IMx, Cytomegelisa II, and FIAX) comparative assays gave positive results; a sample was considered negative if at least two of the three assays were negative. Of the 199 clinical serum samples tested, 194 gave concordant results among the three comparative assays (145 were positive and 49 were negative). The VIDAS results with two samples were persistently equivocal and were therefore excluded from the comparison study. The overall agreement between VIDAS and the established standard was 98.5%. The VIDAS assay yielded one false-positive and two false-negative results. The intra- and interassay precision studies indicate that the VIDAS assay is suitable for clinical use. The VIDAS system is rapid, self-contained, and fully automated and would be useful for screening of cytomegalovirus immune status.