We compared the performance of four assays for detection of hepatitis B virus (HBV) DNA: the PCR; the branched DNA hybridization assay (Chiron); and two hybridization assays that use liquid hybridization (Abbott) or direct membrane hybridization (MH). Testing 109 random hepatitis B surface antigen-positive patient samples, the percentages found to be HBV DNA positive among 30 hepatitis B e antigen (HBeAg)-positive samples and 79 HBeAg-negative samples were as follows: PCR, 100 and 90%; Chiron, 73 and 25%; Abbott, 67 and 13%; and MH, 40 and 8%. In six hepatitis B surface antigen-positive, HBeAg-negative samples, all three hybridization assays detected HBV DNA. Testing dilutions prepared from the Eurohep HBV DNA standards, the detection limits of the assays appeared to be the following: PCR, 2.5 x 10(2) HBV genomes per ml; Chiron, 2.5 x 10(6) genomes per ml; and Abbott and MH, 2.5 x 10(7) genomes per ml. HBV DNA levels in the dilution series, as reported by the Chiron and MH assays, were, on average, 2 times higher than calculated; the Abbott results were, on average, 19 times lower than calculated. We concluded that high levels of HBV DNA and the presence of HBeAg do not necessarily coincide, that the application of hybridization assays is limited to the monitoring of relatively high levels of HBV DNA, and that further standardization of quantitative HBV DNA assays is necessary to facilitate comparison of HBV DNA levels.