Amplification assays for viral genomes are at present too expensive and cumbersome to be applied to individual blood donations. Through constructing interesting pools of specimens, however, it may be possible to screen as a single process large numbers of units for several low prevalence viruses using relatively few tests. The preparation of the intersecting pools that would be required is explained in this paper. If test sensitivity and specificity were adequate, the testing of these pools would permit timely release of components that had the security of genetic testing added to current serological screening programmes. The method also makes screening for other viruses feasible.