BACKGROUND: AML with myelodysplasia related changes (AML MRC) is known to show a poor prognosis compared with de novo AML, but controversies exist about the prognostic impact of multilineage dysplasia (MLD) among MRC. We investigated the prognostic impact of MLD in AML MRC. METHODS: A total of 357 patients newly diagnosed as AML at Asan Medical Center from January 2001 to December 2005 were analyzed. They were diagnosed and classified as AML with recurrent genetic abnormalities, AML MRC, and AML not otherwise specified (AML NOS). Prognostic markers including overall survival (OS) and event free survival (EFS) were obtained through retrospective analysis of electronic medical records. RESULTS: AML MRC patients showed a lower complete remission (CR) rate (44.7% vs. 64.9%, P=0.002) and shorter OS (297 vs. 561 days, P=0.004) and EFS (229 vs. 374 days, P=0.004) than AML NOS patients. Patients with MLD among AML MRC also showed a lower CR rate (37.7%, P=0.001) and shorter OS (351 days, P=0.036) and EFS (242 days, P=0.076) than AML NOS patients. However, among AML MRC patients, there were no differences in OS, EFS and CR between patients with and without MLD. CONCLUSIONS: AML MRC patients showed a lower CR rate and shorter OS and EFS than AML NOS patients. AML MRC patients with MLD showed similar results and their prognosis was not different from those without MLD. MLD findings among AML MRC could be an independent poor prognostic factor in de novo AML.