BACKGROUND: Early detection and treatment of cytomegalovirus (CMV) infection is very important because CMN infection is a major cause of morbidity and mortality after organ transplantation. CMV antigenemia assay has been reported to be very sensitive and specific for detection of CMV infection among many laboratory methods. However, there is no single method correlated well with the infection state up to now. We compared the results of SHARP Signal System Assay (Digene, USA) using PCR and hybridization with those of CMV antigenemia assay (Clonab CMV-kit; Biotest AG, Germany) to evaluate their clinical usefulness. METHODS: We performed SHARP Signal Assay on whole blood samples of 125 from 56 transplanted patients submitted for CMV antigenemia at Samsung Medical Center. We compared the results with those of CMV antigenemia and evaluated the correlation with CMV disease state. RESULTS: Fifty six patients were classified as three groups; 43 patients with no evidence of CMV infection, four patients with CMV infection and 9 patients with CMV disease. Twenty four cases (19.2%) showed discrepant results between the two methods. Of the 22 cases showing positive only by SHARP Signal Assay, two cases were proved to be CMV disease, 12 cases were on antiviral treatment and remaining cases had no evidence of infection. Two cases showing positive only by CMV antigenemia were confirmed to be CMV disease. For CMV disease, the sensitivity of SHARP Signal Assay and CMV antigenemia were 85.7% and 90.5%, respectively and the specificity of them were 73.1% and 93.3%, respectively. CONCLUSIONS: CMV antigenemia is thought to be useful for early diagnosis and follow-up of antiviral treatment as a quantitative and highly specific method, and SHARP Signal Assay can be used as a complementary method because it correlates well with disease state.