OBJECTIVE: To determine the average cost-effectiveness ratios of interferon used first line and imatinib used second line in chronic phase CML. METHODS: A general cost effectiveness analysis was performed. Therefore, a model consisting of two phases is developed: an induction phase of eight months, in which newly diagnosed patients are treated with two different doses of IFN or patients refractory to IFN are treated with imatinib, and a chronic treatment phase where patients are treated according the result of the induction phase. Costs and effects are modelled for a maximum of 25 years. Input for this model was derived from literature and expert opinion. Costs are based on real cost prices and tariffs. RESULTS: Compared to first line IFN, treatment with imatinib second line gives greater quality adjusted life years (QALYs); 4.98 versus 6.67. Average costs of treatment with 5MIU IFN are €76,969 and with 3MIU IFN €53,257. For treatment with imatinib the total costs are €140,765 per patient. Average cost-effectiveness ratios in the 5MIU IFN group is €15,445 per QALY and €10,687 in the 3MIU IFN group. Using imatinib second line the average cost-effectiveness ratio is €21,082 per QALY. CONCLUSION: The addition of imatinib to the treatment options in CML suggests that the costs of treatment will rise but average survival and quality of life will also considerably increase. The average costs per QALY are in our view fully acceptable.