In the majority of cases of overt acute myeloid leukemia (AML), there is no knowledge about a preleukemic phase of myelodysplastic syndrome (MDS). A few recent case-control studies suggest an association between MDS and several occupations. We report a unique case of MDS/AML related to the patient's work condition with numerous cytostatic agents. The karyotype revealed a spectrum of genetic rearrangements identified by conventional cytogenetics, fluorescence in situ hybridization (FISH) and spectral karyotyping (SKY). We suggest that amplification of chromosomal material may play a greater role in leukemogenesis than has been recognized previously.