The objective of this study was to show which species of flies are responsible for human myiasis in the Brazilian state of Goiás and to determine the frequency of cases. Patients at the Clinical Hospital of the Federal University of Goiás (UFG) were examined, and any fly larvae found in their wounds were collected for taxonomic identification. First instar larvae were observed using light microscopy; second and third instars were examined using stereoscopy. The following screwworm flies were observed, in decreasing order of prevalence: Cochliomyia hominivorax, Sarcodexia lambens, Dermatobia hominis, Chrysomya albiceps, Chrysomya megacephala, Lucilia cuprina, and Eristalis tenax. Myiasis was most frequent in the legs in adults, male patients, elderly people, and people of reproductive age. It was lowest in children, females, and patients with neurologic or psychiatric disorders. Frequency was high in patients living in low socioeconomic conditions with poor personal hygiene. Education and sanitation measures are needed to counteract this situation.