Cytogenetic analyses were performed in 72 acute myeloid leukemia (AML) patients > or = 60 years old. Karyotype was normal in 35 (48.6%) patients (group III). 3 patients (4.2%) had favourable karyotype with t(15;17) as an isolated aberration (group IV). 21 patients (29.2%) had adverse karyotypes (group I) and 13 (18%) had intermediate karyotypes (group II). Adverse karyotypes were simple (< 3 aberrations), with add 3q, 5q-, 7q-, in 5 persons, and complex (> or = 3 aberrations) in 16. Karyotypes of 14 patients from the latter group contained > or = 5 aberrations. Laboratory and clinical data were comparable between groups with > or = 3 and with > or = 5 changes. In more than 2/3 complex karyotypes chromosome 5 and 7 aberrations also were found. AML clinical course of group II patients was more similar to that of group I than of groups III and IV. A frequency of complete remissions differed statistically between group I and the others and a frequency of complete and partial remissions together--between I + II and III + IV groups. Overall survival time differed statistically between all groups. There were significantly more patients with secondary AML in groups I and II than in group III. Analysis according to FAB did not show prognostic significance of this classification. Authors conclude that cytogenetics have a fundamental prognostic importance in AML of the elderly and should be taken into account in establishing therapeutic strategies.