Reasons are given for reducing the Heleomyzidae and Sphaeroceridae to a single family, to be known as Heteromyzidae on grounds of priority. Some aspects of morphology and associated terminology are discussed. Difficulties in using male genitalia characters for higher classification are pointed out. The diverse gland-baskets, present on the hind femur of most Borboroides spp. are described and illustrated. The peculiar stridulatory organ on the fore leg of both sexes of Borboroides musica is described. The apparent groundplan characters of the Heteromyzidae are listed. The relationships of the Chyromyidae and Mormotomyiidae to the Heteromyzidae are briefly discussed and each is excluded from the Heteromyzidae. A provisional grouping of the Australasian heteromyzid tribes into subfamilies is put forward. A revised key to the Australian non-sphaerocerine genera of Heteromyzidae is given. Within this broadly defined family, the endemic Australian tribe Borboroidini includes the genera Borboroides (23 species) and Heleomicra (two species). The species of Borboroides are classified into six informal groups to reflect morphological diversity and probable phylogenetic relationships. The following new species are described: Borboroides stewarti, B. musica, B. danielsi, B. lindsayae, B. tonnoiri, B. donaldi, B. perkinsi, B. dayi, B. staniochi, B. helenae, B. doreenae, B. parva, B. menura, B. gorodkovi, B. shippi, B. corynetes, B. petiolus, B. fimbria, B. bulberti, B. merzi, B. acumen, B. woodhilli, Heleomicra lenis. Adults of some species of Borboroides and Heleomicra are attracted to old carrion or marsupial dung or both, and wombat dung is probably a suitable larval medium for some species.