The FAM caspase binding assay kits from ATCC Corporation can be used to determine amounts of active caspases in cells. The FAM-labeled caspase inhibitor can freely diffuse into the cell. Active caspase irreversibly binds the inhibitor. Upon washing the cells, the amount of fluorescence is proportional to the amount of active caspase in the cell. FAM-LETD-fmk (catalog no. 30-1306) is used to detect caspase 8 and FAM-LEHD-fmk (catalog no. 30-1308) is used for caspase 9.