A rapid assay for the quantification of hepatitis B virus DNA in human serum was developed. The principle of the method combines competitive polymerase chain reaction (cPCR) (for the controlled amplification of hepatitis B virus DNA) and scintillation proximity assay (SPA) technology (for rapid detection and quantitation of PCR products). It also incorporates a reproducible and simple method for the preparation of serum DNA suitable for PCR amplification. The assay has a better linear dynamic range than traditional methods that use 32 P to detect PCR products. It was applied to a range of hepatitis B virus (HBV) surface antigen positive (HBsAg+) sera, and shown to be more sensitive than a commercially available HBV DNA kit.