A rapid method of serum treatment is described that can be used for the detection of viral DNA by polymerase chain reaction (PCR). The key feature of the assay is inactivation of inhibitory serum factors by controlled heating of serum. This method avoids DNA extraction. It is very fast and limited sample handling decreases the chances of contamination by exogenous DNA. It has been successfully used for demonstration of parvovirus B19, hepatitis B virus, and human cytomegalovirus DNA in patient sera. Since pathological components in sera from patients with various diseases do not interfere in the assay, it can be used as a sensitive and safe screening assay for DNA viruses in a routine clinical setting.