Abstract
In a patient with chronic erythroleukaemia an isochromosome 17q was identified in all bone marrow metaphases analyzed. In addition, these cells were characterized by hypodiploidy and the presence of 3 different marker chromosomes. Approximately 50 % of dividing cells in the marrow were bizarre‐looking polyploids. The identification by Giemsa banding of i(17q) in this case of erythroleukaemia supports the concept that there are common cytogenetic characteristics among malignant myeloproliferative disorders.