Cytogenetic and molecular studies were performed on 20 interferon-alpha receiving Turkish chronic myelocytic leukemia patients. Four different restriction endonucleases and bcr-G probe were used for southern blot analysis to detect rearrangements of the bcr gene. The RT-PCR method was also applied to detect chimeric bcr/abl mRNA. Seventeen patients showed a chromosomal break within the 5.8 kb M-bcr region by southern blot analysis while three cases out of 20 have not shown any rearrangement. These three cases were further analysed by RT-PCR and they were also found to be carrying the Philadelphia translocation (Ph), However, in four years of follow-up this RT-PCR positivity has disappeared, which suggests an elimination of Ph clone with prolonged interferon-alpha treatment. Am. J. Hematol, 63:85-89, 2000, (C) 2000 Wiley-Liss, Inc.