To study the clinical and cytogenetic characteristics of four patients with myel odysplastic syndrome (MDS) and one with acute myeloid leukemia experiencing t(1; 7) Methods Five patients seen in our hospital from 1992 to 2001 were diagnosed as MDS and acute myelocytic leukemia (AML) according to the French American British (FAB) criteria Chromosomes were prepared using the direct method as well as 24 hou r unstimulated cultures of fresh heparinized bone marrow for each subject, while R banding was used to analyze karyotypes Dual color fluorescence in situ hy bridization (FISH) using SpectrumRed and SpectrumGreen directly labeled chromoso me 1 specific α satellite DNA probe (red) and chromosome 7 specific α sat ellite DNA probe (green) was performed for three cases Results Of the five patients, three had 1;7 translocation due to a long history of expos ure to benzene In three cases, dual color FISH resulted in three red signals and two green ones, in which one red signal adjoining one green signal in 27 6% , 84% and 18 5% metaphases, respectively Conclusions Exposure to benzene may be the cause for Chinese MDS and AML patients with t(1;7 ) translocation The result of dual color FISH convincingly confirmed that the centromere of the derivative chromosome 7p/1q resulting from 1;7 translocation was made up of centromeres from both chromosomes 1 and 7 To study the clinical and cytogenetic characteristics of four patients with myelodysplastic syndrome (MDS) and one with acute myeloid leukemia experiencing t (1; 7) Methods Five patients seen in our hospital from 1992 to 2001 were diagnosed as MDS and acute myelocytic leukemia AML) according to the French American British (FAB) criteria Chromosomes were prepared using the direct method as well as 24 hou r unstimulated cultures of fresh heparinized bone marrow for each subject, while R banding was used to analyze karyotypes Dual color fluorescence in situ hy bridging (FISH) using SpectrumRed and SpectrumGreen directly labeled chromoso me 1 specific α satellite DNA probe (red) and chromosome 7 specific α sat ellite DNA probe (green) was performed for three cases Results Of the five patients, three had 1; 7 translocation due to a long history of expos ure to benzene In three cases, dual color FISH resulted in three red signals and two green ones, in which o ne red signal adjoining one green signal in 27 6%, 84% and 18 5% metaphases, respectively Conclusions Exposure to benzene may be the cause for Chinese MDS and AML patients with t (1; 7) translocation The result of dual color FISH convincingly confirmed that the centromere of the derivative chromosome 7p / 1q resulting from 1; 7 translocation was made up of centromeres from both chromosomes 1 and 7