Caspase-7 has been identified as a major contributor to the execution of apoptosis. Caspase-7 is cleaved by many enzymes, including caspase-3, -6, -8, -9 and granzyme B. Active caspase-7 consists of a heterotetramer of two large and two small subunits. As an effector caspase, caspase-7 cleaves many of the same substrates as caspase-3, including poly (ADP-ribose) polymerase (PARP). The active caspase-7 antibody provides a new tool for identifying apoptotic cell populations in both tissue sections and cultured cells.