Caspases, a group of cysteine proteases, constitute the effector arm of the cell death machinery. There are seven caspases known in Drosophila, three of which contain long amino-terminal prodomains. Although, compared to mammalian caspases, much less is known about the biology of Drosophila caspases, many studies have shown that caspases are essential for programmed cell death in the fly and are likely to be regulated in ways similar to their mammalian counterparts. Studies on fly caspases have revealed some new insights on cell death regulation. For example, the transcript for the fly caspase DRONC is regulated by the hormone ecdysone during programmed cell death in specific tissues. Recent data on DRONC also suggest that some fly caspases may have unique substrate specificities not ascribed to mammalian caspases. The presence of multiple caspases in Drosophila indicates that apoptotic pathways in insects are likely to be as complex as in vertebrates.