Neutrophils with ring-shaped nuclei were found in 12 out of 28 patients with myeloproliferative disease and only rarely in patients with toxaemic granulocytosis and in healthy controls. Nuclear ring formation and hyposegmentation appeared to be significantly related. Recently we became aware of the occasional occurrence of neutrophils with ring-shaped nuclei in patients with myelodysplastic syndromes (MDS) and in chronic granulocytic leukaemia (CGL). Ring formation is a well-known feature of granulopoiesis in rodents. To our knowledge it has not been described in man. We therefore report here on a search for ring neutrophils in peripheral blood smears of patients and controls.