The safety of the use of kidneys procured from a hepatitis C virus (HCV)-positive cadaver donors in transplantation has recently been the subject of controversy. One factor that is important in determining the transmission of the virus and/or viral liver disease is the total viral inoculum to which the renal allograft recipient is exposed as a result of the transplant. We have studied the effect of a standard pulsatile renal preservation procedure and variations of it on the number of viral copies in organs from HCV-positive donors. An HCV-RNA quantitative reverse transcription-polymerase chain reaction (RT-PCR) method was utilized with a recombinant competitive inhibitor substrate added after cDNA synthesis with the PCR primers within the relatively non-polymorphic 5' untranslated region of the HCV genome. Additionally, strain specificity was found to be detectable using a modification of the technique of restriction fragment-length polymorphism (RFLP-PCR), so that virus from the organ donor could be specifically identified and quantified in the recipient. It was observed that standard preservation procedures using pulsatile perfusion were able to eliminate 75% of the virus from the organ in 20 hr. By modifying this procedure to include additional wash steps and a second pulsatile perfusion, greater than 99% of the virus could be eliminated from the kidney. In a related study, we used quantitative PCR to study requirements for filtration of the virus using HCV-positive serum. It was found that a high-flow-rate ultrafilter with a molecular weight cut-off (MWCO) of 300,000 daltons placed in series to the preservation apparatus was very efficient in eliminating the virus from perfusion solution in less than 2 hr. It can therefore be proposed that with the use of these molecular techniques, pulsatile perfusion coupled with additional viral depletion steps (dilution, and/or filtration) may allow the practical reduction of HCV transmission risk in recipient follow-up studies. The means are thereby presented for similar manipulation of other known or, as yet, unknown transmissible agents.