The tandem repeat of a 28-base-pair (bp) sequence downstream of the human c-Ha-ras-1 oncogene was studied as a probe for DNA fingerprinting. Multiple hypervariable patterns were observed by Southern hybridization at low stringency. The patterns were specific to individuals, indicating the availability of the 28-bp repeat as a probe for DNA fingerprinting. Moreover, we cloned the tandem repeat of a 33-bp sequence, which cross-hybridized with the 28-bp repeat. This 33-bp repeat detected another set of hypervariable restriction fragments by Southern hybridization at the same stringency. These results suggests that 'probe walking' can be employed to develop novel probes that provide different DNA fingerprints.