Survivin, a unique member of the inhibitor of the apoptosis protein (IAPs) family, is over-expressed in many cancers but not in normal differentiated adult tissues. Using semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR), we investigated patterns of survivin gene expression in a group of 12 patients with chronic myeloid leukemia (CML) representing both chronic and blastic phases of the disease. All 6 patients in chronic phase CML were uniformly negative for the survivin transcript, in contrast to 4 Philadelphia chromosome-positive (Ph+) CML patients in blastic crisis, all of whom (100%) were positive for survivin with tangible levels of expression. However, survivin expression was markedly down-regulated in 2 atypical CML patients with Philadelphia chromosome-negative (Ph-) blastic crisis. Our data indicates that up-regulation of survivin expression may be involved in typical CML evolution from the chronic into the blastic phase of the disease.