A quality assurance program has been established by the European Group for Rapid Viral Diagnosis and the European Expert Group on Viral Hepatitis for monitoring nucleic acid detection methods for hepatitis B virus (HBV) DNA in serum samples. Thirty-nine laboratories participated in this quality program and generated 43 data sets. Of the participating laboratories, all but one used the PCR technique to detect HBV DNA. A coded panel was tested that was composed of seven undiluted HBV DNA-positive serum samples and five HBV DNA-negative donor serum samples. Furthermore, two dilution series, one from a positive patient and one from a full-length recombinant DNA, were included. Twenty-six data sets (60.5%) had faultless results with both dilution series. Twelve data sets (27.9%) recognized the undiluted serum samples, and 19 data sets (44.2%) had false-negative and/or false-positive results. Ten data sets (23.3%) performed well with the entire panel of samples. From these results, it can be concluded that in a large group of laboratories HBV detection by PCR shows specificity and sensitivity problems; therefore, PCR test interpretation should be done with great care.