We started to investigate the RUNX1 gene by FISH with the probe “LSI AML1-ETO”, designed to detect the translocation t(8;21), recurrent in acute myeloid leukaemia (AML): it revealed a signal of RUNX1 on the der(21) less intense compared to the normal 21. This evidence concerns the gene RUNX1T1 and acute myeloid leukemia.