A recently introduced method for the detection of hepatitis B viral (HBV) DNA in the serum, using solution hybridization, was assessed for its sensitivity and specificity in 242 sera from patients with chronic HBV infection, and in controls. In 87 sera the results were compared with the classical dot-blot technique. The new method gave positive results in 82% (56/68) of all dot-blot-positive sera and in 97% (35/36) of those with strong positive dot-blot reactions. All 30 hepatitis B surface antigen (HBsAg) carriers positive for hepatitis B e antigen (HBeAg) were positive in the solution hybridization assay, with a mean HBV-DNA level of 172 +/- SE 36 pg/ml. Negative results were obtained in all 20 subjects negative for all HBV markers and in all 36 HBsAg+/anti-HBe+ carriers with normal aminotransferase activity, negative for hepatitis B core antigen (HBcAg) expression in the liver. By contrast 93% (66/71) of the anti-HBe+ patients with positive HBcAg expression in the liver were positive for serum HBV-DNA in the solution hybridization assay, with a mean level of 30.5 +/- SE 6.7 pg/ml. Of 14 sera with discrepant HBV-DNA results in the two assays, 12 were solution hybridization-negative/dot-blot-positive and 2 were solution hybridization-positive/dot-blot-negative. These results indicate that the new, simple method is specific, and suitable for the determination of serum HBV-DNA in clinical practice.(ABSTRACT TRUNCATED AT 250 WORDS)