The prognostic value of cytological features was assessed in 132 patients with de novo acute myeloid leukaemia (AML) treated by anthracycline-cytosine-arabinoside combination chemotherapy. Of these patients, 98 (75%) achieved complete remission (CR). A significantly lower CR rate was seen in patients with trilineage dysmyelopoiesis (TDMP) (P = 0.003), but not in patients with dyserythropoiesis and/or dysgranulopoiesis without abnormal megakaryocytes. Other unfavourable factors were age greater than 50 years (P = 0.042), leucocyte count greater than 100 x 10(9)/l (P = 0.006), M5 FAB subtype (P = 0.013), presence of complex cytogenetic rearrangement or abnormalities of chromosome 5 and/or 7 (P = 0.001). Bone marrow eosinophilia greater than 3% was significantly associated with a higher CR rate (P = 0.04). In a multivariate analysis, a low CR rate was best predicted by the presence of a complex karyotype or abnormalities of chromosome 5 and/or 7 (P = 0.0001) and by the TDMP (P = 0.0036). Median actuarial disease-free survival (DFS) was 24 months. Actuarial DFS was significantly shorter in patients with TDMP (P = 0.0001) and an elevated leucocyte count (P = 0.02). Age, FAB subtype and karyotype had no significant incidence on DFS. Presence of TDMP appears to be an important prognostic factor in de novo AML. This could be used as one of the guidelines to therapy.