National and regional population-based registries are, provided diagnostic accuracy and full coverage of the target population, indispensible tools for epidemiological research. Chronic myeloid leukaemia (CML) registries with more comprehensive reporting may also provide complementary data on treatment outcome to those obtained from clinical trials. Reports from several European CML registries consistently show a crude annual incidence of 0.7-1.0/100,000, a median age at diagnosis of 57-60 years and a male/female ratio of 1.2-1.7. The incidence of CML has been stable over time. Worldwide, variations in the reported incidence of CML may be due to methodological issues, but a true difference between different geographical areas and/or ethnical subgroups cannot be excluded. The prevalence of CML is not well known but has been estimated to be 10-12/100,000 inhabitants with a steady increase due to the dramatic improvement in survival of these patients. In recent population-based studies, CML patients have an overall survival that is comparable to that shown in large clinical trials, though relative survival in patients >70 years is still decreased. The importance of socio-economic factors and health-care setting for outcome and the possible increased risk of secondary cancer in CML are areas of ongoing research.