Karyotype analysis of a case of acute megakaryoblastic leukaemia revealed an X;6 translocation as the sole abnormality. Using fluorescence in situ hybridisation on leukaemic metaphases we demonstrated that the breakpoint on the X-chromosome occurred at p11.21, within a region spanned by a YAC probe which has also been found to be disrupted in synovial sarcomas and some papillary renal cell carcinomas.