The use of flow cytometric techniques has significantly aided the rapid advancement of our understanding of the process of apoptosis. Our laboratory is currently involved in investigating the ways in which cells can be induced to die and some of the signals that may be involved. To this end, we are using flow cytometry to detect apoptosis in cell cultures and to measure intracellular changes that occur during apoptosis, in particular, alterations in parameters such as mitochondrial function, oxidative stress, and gene expression. In this review of recent and ongoing research in our laboratory, we outline our studies on mechanisms of apoptosis by cytotoxic drugs, particularly in relation to the involvement of oxidative stress. In addition, we are studying the increased sensitivity to apoptosis seen in K652 cells that have been transfected with the p53 gene.