A case of abnormal chromatin clumping (ACC) which arose during the course of a myelodysplastic/myeloproliferative syndrome is described in a 61 year old woman who died of haemorrhage 43 months after diagnosis. Mature granulocytes exhibited the same nuclear abnormality described in other patients reported. Unusually, she presented with advanced splenomegaly and lymphadenopathy. This case was the third example of ACC in lymphocytes, the first with clinically confirmed lymphadenopathy. Diagnosis of this subset can be based on: older age; short duration of symptoms; no specific karyotypic damage; non-rearranged bcr; proliferative growth pattern in vitro; numerous circulating myelocytes; profound thrombocytopenia.