Epigenetic silencing of sFRP genes has been shown to lead to constitutive activation of the canonical Wnt-signaling pathway. The first description of deregulated Wnt-signaling activation in a hematological malignancy was reported in chronic myeloid leukemia (CML). To investigate whether epigenetic silencing of sFRP is responsible for the observed Wnt activation in CML, we studied the methylation and mutational status of the sFRP1 promoter in 48 chronic phase CML patients. Of the 48 CML patients 41 were shown to be unmethylated, 6 patients hemi-methylated and 1 patient fully methylated at the sFRP1 promoter. Albeit observed infrequently in chronic phase CML, sFRP1 promoter methylation correlated with primary cytogenetic resistance to imatinib mesylate. sFRP1 promoter methylation may indicate a genetically more unstable form of disease resistant to therapy and provide a key biological difference in therapy resistant patients, in addition to a possible mechanism for the observed activation of canonical Wnt signaling in CML.