It is well recognized that malignant cells from acute lymphoblastic leukemias (ALLs) generally yield less satisfactory metaphases for analysis than cells from other diseases when standard laboratory processes are applied, in spite of the fact that karyotypically normal cells from the same sample can produce high-quality divisions under the same conditions. Thus it is of primary importance in the analysis of ALL preparations not simply to select the best available metaphases for analysis, or the malignant clone may not be sampled. In addition to this, some variation to routine procedures may enhance the quality and relative quantity of abnormal metaphases and facilitate accurate analysis.