Objective:To delineate the G-banding-sug gested chromosome translocations by fluorescence in situ hybridization (FISH ) technique. Methods: Locus-specific probes, generated by degen erate oligonucleotide-primed PCR (DOP-PCR) technique from yeast artificial chr omosomes (YACs) mapping the regions in question, were used for FISH tests. Results: Among the 2 cases unresolved by G-banding, FISH confirm ed that one had a balanced translocation between chromosome 11 and chromosome 13 , the other had an unbalanced translocation between chromosome 6 and chromosome X.Conclusion: Because of its high sensitivity and specificity, FISH technique is a powerful adjunct to chromosome banding techniques, particula rly for the delineation of subtle chromosome rearrangement(s) and the origin of segment(s).