The detection of dysplastic features of hematopoiesis in de novo acute myeloid leukemia (AML) by light microscopy is defined as AML with trilineage myelodysplasia (AML/TLMD). The prognostic relevance of these dysplastic features for patients with de novo AML remains unclear. In order to evaluate the role of dysplasia in de novo AML, bone marrow aspirates from 69 patients were analyzed prospectively and investigated separately for erythropoiesis, granulopoiesis and megakaryopoiesis by three independent investigators. The overall complete remission (CR) rate was 48.8% and partial remission (PR) or nonresponders constituted 52.2% of the patients investigated. The median overall survival time was 5 months with a disease-free interval of 3.5 months for all patients. Dysgranulopoiesis (DysG) was observed in 30.4%, dysmegakaryopoiesis (DysM) in 50.7%, and dyserythropoiesis (DysE) in 43.5%. Of all patients, 26.0% showed trilineage dysplastic features and were thus classified as AML/TLMD. A significantly worse prognosis (Kaplan-Meyer plot, Student's t-test) was calculated for those patients with detection of only DysG (p = 0.002), DysM (p = 0.02), DysE (p = 0.04) as compared with patients without any dysplastic signs. An unfavorable karyotype was correlated with patients showing DysG (P = 0.02) and DysM (P = 0.04). For these patients with an unfavorable karyotype, the occurrence of any dysplastic features had no additional prognostic impact. Dysplastic features (DysG, DysM, DysE) seem to be an important prognostic factor in de novo AML correlating with short overall survival. DysG and DysM correlated well with the appearance of unfavorable chromosomal abnormalities. It may be reasonable to assume that patients with dysplastic features should be considered for more aggressive treatment schedules at the time of diagnosis.