Myeloid leukemia cell lines demonstrate reproducibility and accuracy of in vitro flow cytometric apoptosis assays. Cells from myeloid leukemia cell lines were cultured in the presence or absence of varying doses of DNR or ARA-C, or were treated with RAD and prepared for flow cytometric analysis as described in Materials and Methods. Cells of the ML1 cell line (wild-type p53, low BCL-2 expression) showed distinct cell-cycle perturbations (A) and reproducible treatment-associated sub-G1 apoptosis (A and B) after treatments with DNR, ARA-C, or RAD. Dose-responsive apoptosis was confirmed in other commonly used apoptosis assays, including Trypan blue staining demonstrations of membrane permeability and microscopic presentations of abnormal fluorescent nuclei (B). In contrast, KG1a cells (mutant p53, high BCL-2 expression) showed significantly less apoptosis in all assays of apoptosis (B). *Doses of each treatment shown to be equitoxic in Trypan blue exclusion assays of ML1 cells. These doses were used for treatments of cells in control bone marrow and AML samples.