We report a case of a 27-year-old man with Ph1-positive chronic myelogenous leukaemia (CML). At the time of diagnosis 100% Ph1-positive cells were found with a trisomy 8 in 50% of them. In absence of therapy, his haematological status remained stable for 3 years. Subsequently a progressive regression of haematologic and cytogenetic data was observed. Eight years after diagnosis the karyotype showed only 37% Ph1-positive cells and the trisomy 8 had disappeared.