Fluorescence in situ hybridization (FISH) using chromosome-specific plasmid libraries and chromosome region-specific DNA markers allowed the characterization of a t(10;22;11) (p11.2;q12;q24) in a Ewing's sarcoma (ES). This study illustrates the usefulness of molecular cytogenetic analysis of ES, especially for determining the localization of the translocated 11q24-25 segment in complex or variant translocations.