Disruption in circadian gene oscillations has previously been shown for the clock genes (Per1, Per2, Per3, Cry1, Cry2 and CKIe) in CML patients, and partial recovery of oscillation in these genes was seen in patients that demonstrated both complete cytogenetic response (CCyR) and major molecular response (MMR) following treatment with imatinib [10]. The gene discussed is PER2; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.