In Ph(+) CML patients who achieved complete cytogenetic response (CCR) with interferon-alpha (IFN) treatment, how long the treatment should be continued has not well been investigated. We report here 2 CML cases who stopped the treatment after CCR had been sustained with IFN for 2-3 years. A 49-year-old male (case 1) achieved CCR 6 months after the initiation of IFN treatment. CCR had been maintained for 3 years, and then the treatment was ceased. CCR has been sustained without any therapy for 4 years. In this case, RT-PCR became negative half a year after achievement of CCR, and since then negative RT-PCR has been maintained. In case 2, a 50-year-old male, CCR was achieved after 8 years of IFN treatment, and maintained for 2 years. One month after cessation of the treatment, CML relapsed cytogenetically. In case 2, negative RT-PCR results were not maintained during the period of CCR. In case 1, the levels of T-cells for PR 1 were undetectable in the peripheral blood.