Ready-to-use fluorometric substrate for FLICE/caspase-8 and related caspases that recognize the amino acid sequence IETD. The sequence IETD is based on caspase-8 cleavage site in CPP32/caspase-3 proenzyme. FLICE and related caspase activity can be quantified by fluorescent detection of free AFC after cleavage from the peptide substrate IETD-AFC at Ex. = 400 nm and Em. = 505 nm, using a fluorometer or multi-well fluorescence plate reader. Alternatively, a shift in fluorescence from blue to green upon cleavage can be visualized using a hand-held long-UV lamp.