DNA fingerprinting is a very powerful tool that enables specific identification of individuals. In order to study fingerprinting patterns in the Chinese, the oligonucleotide probe designed by Epplen et al was used. Peripheral blood leukocyte DNA was digested with restriction enzyme Hinf I and probed by (GTG)5. Normal females and males were tested; all revealed very different DNA fingerprints. Most of the discernible bands in the gel were polymorphic; there was no specific association between any polymorphic band and the sex of the individual tested. In situ gel-hybridization was used with the oligonucleotide probe, and after electrophoresis, all procedures could be completed within one working day. Three patients who had received bone marrow transplants from their respective siblings had the same fingerprints as their donors. The inheritance of all bands from either the father or mother proved parents' authenticity. DNA fingerprinting with a oligonucleotide probe is obviously a useful technique. Clinical application may include engraftment monitoring, zygosity determination and paternity testing.