A patient with acute myelocytic leukemia in relapse presented with t(16;21) (p12;q22). Hematologic studies revealed a large number of abnormal eosinophils in the bone marrow. The complexity of chromosome #16 rearrangements associated with acute nonlymphocytic leukemia and the possible significance of chromosomes #16 and #21 in relation to the concomitant eosinophilia are briefly discussed.