The molecular relapse after imatinib discontinuation is defined by positive PCR for BCR-ABL two times using RTQ-PCR with increasing of the transcript on two following assessment and or a value> 0.1% i.e. lost of MMR. In case of molecular relapse it is recommended to re-challenge an imatinib treatment. According to our experience the 50 patients well documented who re challenged the treatment were sensitive again. The treatment of molecular relapse by second generation tyrosine kinase inhibitors (dasatinib or nilotinib) will possible in the current trial. It is important for all the French patients to be included in a national trial to avoid discontinuation without evaluation.