Biological transmission of eggs and larvae of the human bot fly Dermatobia hominis by a female of the horn fly Haematobia irritans is reported for the first time in South America. Seventeen females of H. irritans were collected near the municipality of Morada Nova (19S, 45W) in the Três Marias, region of northwestern Minas Gerais in June 1993 and sent to the Entomology Laboratory, Dept. of Prevention Veterinary Medicine, Veterinary School of the Federal University of Minas Gerais for identification based on the keys of B Greenberg.