In this report we describe a sensitive HIV-1 detection method which is applicable for confirmation testing of donors whose blood sample gives indeterminate viral-serology results. The method involves performing a polymerase chain reaction (PCR) and detecting the generated fragments using liquid hybridization and gel retardation. We found that it is as specific as blotting on a filter and hybridization with an internal probe but at least tenfold more sensitive. After applying it on DNA samples of a panel of 11 persistent indeterminate anti-p24^gag-reactive donors, none was found to be PCR positive. Considering other negative virological and biochemical test results and case-historical data, these donors are not likely to be HIV-1 infected.