Activation of ICE-family proteases/caspases initiates apoptosis in mammalian cells. The Caspase-5 Fluorometric Assay Kit provides a simple and convenient means for assaying the activity of caspase-5 and related caspases that recognize the sequence WEHD. The assay is based on detection of cleavage of substrate WEHD-AFC (AFC: 7-amino-4-trifluoromethyl coumarin). WEHD-AFC emits blue light (λmax = 400 nm); upon cleavage of the substrate by caspase-5 or related caspases, free AFC emits a yellow-green fluorescence (λmax = 505 nm), which can be quantified using a fluorometer or fluorecence microtiter plate reader.