The xenotropic murine leukemia virus-related virus (XMRV) was first described as a novel human gammaretrovirus in prostate tumor tissues and was reported to be found in blood, suggesting the possibility of XMRV transmission via blood transfusion. The gag and env regions of the XMRV proviral DNA that were detected 1,030 blood samples collected from the greater Tokyo area were examined by real-time PCR analysis. However, XMRV infection was not found in the samples; this suggested that the risk of XMRV transmission via transfusion is very low in Japan.