Myiasis is the infestation of living vertebrates by fly larvae that feed for at least part of their development on the host's dead or living tissues, body substances, or ingested food. The occurrences of traumatic myiasis in humans and animals in urban and rural environments represent serious economic and public health concerns. This study reports a 49-year-old tracheostomized man undergoing chemotherapy treatment who was parasitized in the hospital in São Gonçalo, Rio de Janeiro, Brazil, by larvae of the screwworm, Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae) in the thoracic cavity.