Conventional cytogenetic is the standard technique for detection of Philadelphia (Ph) chromosome in chronic myeloid leukemia (CML). Evaluation of abelson murine leukemia/breakpoint cluster region (abl/bcr) fusion using dual-colour fluorescence in situ hybridization (D-FISH) is an alternative approach allowing rapid and reliable detection of the disease. We employed the technique of interphase D-FISH to detect the abl/bcr fusion in 21 patients and the results were compared to those of conventional cytogenetic analysis. A significant agreement was observed between the results, indicating the accuracy of interphase D-FISH. The technique can overcome the disadvantage of conventional cytogenetic methods, which depends on cell culture and analysis of banded chromosomes, since the analysis is performed by signal counting on uncultured target cells. Furthermore D-FISH provides a more reliable method for evaluating the degree of clone remission to patients with CML after therapy compared to the conventional cytogenetic analysis.