Some species of calliphorid blowflies lay their eggs in wounds; their larvae develop by feeding on the tissue, and the infection is known as myiasis or fly-strike. But wounds, from whatever cause, are frequently contaminated with bacteria - many o f which can spread in the bloodstream causing septicaemia and/or toxaemia. For example, wound contamination with Clostridium welchii - leading to 'gas gangrene' - was a frequent cause of death amongst battlefield casualties. It is from such situations that early observations were made on the beneficial effect of some blowfly larvae in limiting the bacterial infection of wounds. Indeed, some military surgeons would deliberately infest wounds with blowfly maggots in order to prevent bacterial complications. Now, a century or two later, the search for new antibiotics had led researchers back to these early observations, and in this article, Gory Erdmann describes progress in understanding the antibacterial action of blowfly maggots.