The Tribioscience Caspase-Family Colorimetric Assay Kits provides a simple and convenient means for assaying the activity of caspases family members (caspase-1, 2, 3, 4, 5, 6, 8, 9 and 10). The assay is based on spectrophotometric detection of the chromophore p-nitroaniline (pNA) after cleavage from the labeled substrate. The pNA light emission can be quantified using a spectrophotometer or a microtiter plate reader at 400- or 405-nm. Comparison of the absorbance of pNA from an apoptotic sample with an uninduced control allows determination of the fold increase in caspase-family member activity.