The morphological changes typical of apoptosis, as well as the loss of integrity of the plasma membrane and the breakdown of nuclear DNA provide numerous features that permit recognition of apoptotic cell death by various methods. Flow cytometry (FCM) and laser scanning cytometry (LSC) allow for accurate and rapid measurement of apoptosis in both cultures and clinical samples (e.g. solid tumors, bone marrow aspirates, peripheral blood etc.). Furthermore, both FCM and LSC enable one to correlate the apoptosis with the position of the dying cell in the cell cycle. Discussion includes the cytometric identification and quantitation of apoptotic or necrotic cells, based on the analysis of a particular biochemical or molecular feature that is characteristic for either necrosis or apoptosis.