Long ago, some doctors noticed soldiers that had maggots on their wounds healed quicker than those without maggots. Maggots eat the dead skin cells and bacteria. Maggot Therapy (also known as Maggot Debridement Therapy (MDT), larval therapy, larva therapy, or larvae therapy) is the intentional introduction of live, disinfected maggots or fly larvae into non-healing skin or soft tissue wounds of a human or other animal. This practice was widely used before the discovery of antibiotics, as it serves to clean the dead tissue within a wound in order to promote healing.

Some types of maggots found on corpses can be of great use to forensic scientists. By their stage of development, these maggots can be used to give an indication of the time elapsed since death, as well as the place the organism died. The size of the house fly maggot is 9.5-19.1mm (3/8 to 3/4 inch). At the height of the summer season, a generation of flies (egg to adult) may be produced in 12-14 days.

Maggots are classified using "instar" stages. An instar I is about 2-5 mm long; instar II 6-14 mm; instar III 15-20 mm. These correspond to an age of 2-3 days, 3-4 days, and 4-6 days (for average house flies or bottle flies) since the eggs were laid. Some forensic scientists use this data to determine the approximate time of death of a human body.

Some maggots cause damage in agricultural crop production, including root maggots in rapeseed and midge maggots in wheat. Some maggots are leaf miners.

Maggots are bred commercially, as a popular bait in angling, and as a food for carnivorous pets such as reptiles or birds.