Abstract
The blood and bone marrow of a 75-year-old woman with eosinophilia were studied in an attempt to characterize further the entity eosinophilic leukaemia (EL). Haemopoietic cell culture in agar gave patterns of colony size and number and cell morphology indistinguishable from those seen in classical chronic granulocytic leukaemia (CGL). Analysis of myeloid cells showed an extra C group chromosome that proved on Giemsa banding to be number 10. These results suggest that some cases of EL represent a chronic myeloproliferative disease that resembles classical CGL but can be distinguished from it by chromosomal analysis.