Chromosomal abnormalities are of significance in the study of hematologic malignancies. We describe one case of myelodysplastic syndrome (MDS) diagnosed 22 years ago as polycythemia vera (PV) as well as a case of unclassified myeloproliferative disease (MPD) with a poor clinical course. Both patients presented del(11)(q13) as the sole clonal abnormality. This abnormality was also found in two additional cases of MDS. Summarizing the literature, only ten other cases of myeloid malignancies with deletion of 11q involving band q13 as the sole anomaly have been reported. All but one of these cases presented interstitial deletions.