Annexin V-FITC kit allows fluorescent detection of annexin V bound to apoptotic cells and quantitative determination by flow cytometry. The AnnexinV-FITC kit uses annexin V conjugated with fluorescein isothiocyante (FITC) to label phosphatidylserine sites on the membrane surface. The kit includes propidium iodide (PI) to label the cellular DNA in necrotic cells where the cell membrane has been totally compromised. This combination allows the differentiation among early apoptotic cells (annexin V positive, PI negative), necrotic cells (annexin V positive, PI positive), and viable cells (annexin V negative, PI negative).