We documented the occurrence and severity of dyserythropoiesis as an artifact of storage in bone marrow aspirates collected in EDTA. Bone marrow samples were obtained from 7 patients without myelodysplasia. Specimens were stored at room (20 degrees C-24 degrees C) or refrigerated (1 degrees C-6 degrees C) temperature and examined for dyserythropoiesis at 0, 1, 2, and 3 days. Initial specimens showed few dyserythropoietic abnormalities; nuclear aberrations occurred in 1.07%+/-0.06% (mean +/- SEM) of the erythroid population. At room temperature, dyserythropoietic changes increased significantly with each day of storage. Nuclear and cytoplasmic alterations occurred; the former are diagnostically more important in the diagnosis of myelodysplastic syndromes. Cytoplasmic changes were more extensive than nuclear abnormalities. The mean +/- SEM percentage of erythroblasts with cytoplasmic vacuoles increased with each day of storage: day 0, 1.1%+/-0.2%; day 1, 22.1%+/-1.8%; day 2, 29.4%+/-2.0%; day 3, 35.6%+/-1.9%. Nuclear shape changes increased to 6.21%+/-1.12%, 11.36%+/-1.12%, and 12.85%+/-1.20% on days 1, 2, and 3, respectively. After 1 day of storage, sufficient dysplastic changes occur to cause difficulty in the diagnosis of a myelodysplastic syndrome. Changes are inhibited significantly by refrigerated storage.