The natural history of chronic myelogenous leukaemia has changed in recent years, partly as a result of earlier diagnosis but mostly as a consequence of the availability of effective therapies that have the potential to eradicate the Philadelphia-positive clone. The prognostic models designed in the pre-interferon-alpha (IFN-alpha) era based on clinical characteristics of the disease are still useful in identifying different risk groups after treatment with IFN-alpha, but achieving a cytogenetic response with IFN-alpha is now the most important prognostic factor for survival. The significance of other molecular and biological variables remains to be determined.