Spectral karyotyping (SKY) was performed in patients with acute myeloid leukemia (AML; n = 25), secondary AML (s-AML; n = 7), myelodysplastic syndrome (MDS; n = 6) and s-MDS (n = 1) to complement conventional cytogenetic investigations. According to the results of conventional cytogenetics the patients were subdivided into three groups: group 1, normal karyotype, n = 19 cases, median age = 64 years; group 2, patients displaying either one or two single aberrations, n = 10 cases, median age = 54 years; group 3, patients with > or =3 independent aberrations, n = 10 cases, median age = 61.5 years. SKY identified no abnormal metaphases in group 1. In one patient of group 2 a hidden translocation t(7;14)(q3?1;q2?2) could be revealed with SKY. Conventional cytogenetics had only shown trisomy 8. A similar t(7;14) was also detected in one patient of group 3. SKY was helpful for the delineation of marker chromosomes and additional material. Furthermore, SKY could distinguish between partial and total monosomies or real existing and apparent deletions. The combination of G-banding, FISH and SKY was found very useful for the precise delineation of the karyotype. As a result of our study we recommend SKY investigation as an important additional tool for accurate chromosome analysis. The detected t(7;14) might represent a novel recurrent translocation in acute myeloid leukemias.