Chromosomal data from 82 informative, unrelated Ewing's sarcoma (ES) specimens (including 20 personal specimens) were reviewed for secondary changes additional to the t(11;22)(q24;q12). Additional numerical and/or structural changes were found in 75 specimens. Trisomy 8 was observed consistently in half of the 43 cases selected for analysis of numerical changes. A nonrandom der(16) was observed as a result of an unbalanced t(1;16) in 18% of the 82 analyzed for structural changes. Consistent involvement of chromosome #16 in rearrangements with chromosome #1 may be an additional chromosome change specifically associated with ES.