Foetus is the primary musical outlet of J. G. Thirlwell. Until 1995 the band underwent various name changes, all including the word foetus. Monikers adopted at different times include Foetus Under Glass, You've Got Foetus On Your Breath and Scraping Foetus Off The Wheel. After 1995 the name permanently became Foetus, though the related project The Foetus Symphony Orchestra was founded in 1997 and continues.

Thirlwell acts as the sole instrumentalist, vocalist, songwriter and producer for all Foetus works and as such is the only member of the band. Other artists may occasionally collaborate with Thirlwell on Foetus works but are not considered members of Foetus. Thirlwell is solely responsible for the musical output of the band.

J. G. Thirlwell has many side-projects, in which he frequently goes by the name Clint Ruin. One such grouping is Wiseblood with former Swans member Roli Mosimann. The material tends toward the realm of the darkest and most sexual Foetus songs, with Mosimann's Swans lineage showing in the slow, crushing pacing of many tracks. Thematically, Wiseblood's lyrics center around the misanthropic exertion of power, typically via murder, sex or assault. Wiseblood existed on-and-off from the mid-1980s through early 1990s.

Thirlwell has released singles as Foetus Under Glass, Phillip & His Foetus Vibrations, Foetus Over Frisco, Foetus Art Terrorism, You've Got Foetus On Your Breath, Foetus Über Frisco, The Foetus All Nude Revue, Scraping Foetus Off The Wheel, Foetus, Inc., and Foetus.

In terms of full length studio albums, Thirlwell has issued material Scraping Foetus Off The Wheel, You've Got Foetus On Your Breath, and Foetus, as well as Foetus Interruptus and The Foetus Symphony Orchestra. Live albums have been credited to Foetus and Foetus, Inc., as well as Foetus Corruptus and Foetus in Excelsis Corruptus Deluxe.

Other name variations exist, but are more difficult to come by. A 1981 compilation appearance credits the artist as Foetus In Your Bed. Two previously unreleased tracks on the 1989 compilation Sink are credited to Foetus Eruptus. A guest appearance on Marc Almond's 1983 Marc and the Mambas album is credited to Jim Foetus and The Transvestites From Hell.

Finally, in 1985, the band issued a box in which to house their various releases; the box contained no music, but was credited to The Foetus Of Excellence. The front cover also listed the various Foetus-based aliases under which Thrilwell had recorded, and would record in the future. In addition to almost all the above names, three name variations were included that have not (to date) issued any material: Foetus Über Alles, Foetus Flesh and Foetus On The Beach. Foetus On The Beach was scheduled to release a triple album in 1985, and even had a catalogue number assigned to the project, but the work remains unissued.

All full-length Foetus album titles are four-letter, one-syllable words, often with multiple connotations.

The artwork of Foetus releases shows a deliberate progression of colour: the earliest releases are black and white, with the addition of red on the Deaf album, and further addition of yellow on Nail. Full-color art was introduced on Gash. Beginning with Flow, the artwork of primary albums reverted to black/white/red, though other releases continue in full colour.