The polymerase chain reaction was used to amplify rearrangements of T-cell receptor gamma genes from 2 leukemic DNA samples involving the same variable segment. One V-J junction was sequenced and an anti-junctional oligonucleotide synthesized. This oligonucleotide was used as probe on in vitro amplified DNA. We show that this strategy allows the detection of the corresponding clonal DNA at dilutions of up to 10(6) fold in germline DNA. Moreover we demonstrate that it is possible to differentiate this clone from the second leukemic clone and from polyclonal T-cells.