Abstract: To ascertain genomic alterations associated with Imatinib resistance in chronic myeloid leukaemia, we performed high resolution genomic analysis of CD34+ cells from 25 Imatinib (IM) resistant and 11 responders CML patients. Using patients’ T-cells as reference, we found significant association between number of acquired cryptic copy number alterations (CNA) and disease phase (p =0.036) or loss of IM response for patients diagnosed in chronic phase (CP) (p =0.04). Recurrent cryptic losses were identified on chromosomes 7, 12 and 13. On chromosome 7, recurrent deletions of the IKZF1 locus were detected, for the first time, in 4 patients in CP. [Copyright &y& Elsevier]