A group of 201 adult patients, 127 younger and 74 older than 55 years, with de novo acute myeloid leukemia were investigated to determine the prognostic significance of karyotype on early death (toxic or aplastic death occurring before hematopoietic recovery), drug resistance, continuous complete remission (CCR) and survival probabilities at 5 years. A good prognostic impact was found for t(8;21), t(15;17) and inv(16). The best factor proved to be t(8;21) (5-year survival probability: 50%), followed by t(15;17) (5-year survival probability: 39%) and by inv(16) (5-year survival probability: 43%). An intermediate outcome was found in patients with trisomy 8 (27% alive at 5 years) and in patients with numerical abnormalities other than -7 and +8 (33% in CCR and 62% alive at 5 years). Normal karyotypes had a different prognostic impact according to age: intermediate in young and good in older patients. A poor outcome was observed among patients with del(5q)/-5 (median survival: 1 month), with 11q23 rearrangements (median survival: 1.5 months) and with del(7q)/-7 (median survival: 10 months). The 'other structural change' group was also found to be a poor risk population (5-year survival probability: 5%) whereas complex karyotypes were predictive of short survivals only in older patients. Conversely, del(7q)/-7 and +8 as secondary changes, had no prognostic impact.