Killers is the only Iron Maiden album to feature two instrumentals and was written almost exclusively by Steve Harris, with only minor assistance from the rest of the band (the title track and "Twilight Zone" being the only other songs to receive additional writing credits). Each song, with the exception of "Murders in the Rue Morgue", based on the story of the same name by Edgar Allan Poe, and "Prodigal Son", had been written in the years prior to the recording of their debut album, although none were recorded professionally until the Killers sessions, apart from "Wrathchild" (an early version recorded in 1979 was featured on the Metal for Muthas compilation).
The US edition, which came out a few months after it did in the UK, was initially released on Harvest Records/Capitol Records and subsequently on Sanctuary Records/Columbia Records. "Twilight Zone" was also added to the album.
The Killer World Tour was the tour in support of the album and would feature the band's earliest shows in the US, the first being at The Aladdin, Las Vegas in support of Judas Priest.