The results of a comparison of three DNA-detection methods for human parvovirus B19 DNA are described. The sensitivity of detection of virus from hybridization assays using 32P-radiolabeled DNA and RNA probes was compared with a method for enzymatically amplifying specific target DNA sequences (polymerase chain reaction). B19 virus DNA was detected using a radiolabeled DNA probe at serum dilutions of 10(-3), equivalent to approximately 3 pg of viral DNA. Using radiolabeled RNA probes even 0.3 pg of viral DNA was detectable. The polymerase chain reaction was more sensitive than the hybridization assays: 100 fg of viral DNA was easily detectable by electrophoresis on agarose and after subsequent hybridization with a radiolabeled probe approximately 10 fg of B19 DNA was detected. The sensitivity of the PCR, combined with the simplicity and reduced time scale, demonstrates the potential of this technique as an additional method for routine diagnosis of B19 infections.