|Kat was founded in 1979 by guitarist Piotr Luczyk and drummer Ireneusz Loth. Shortly after they were joined by bassist Tomasz Jaguś and another guitarist, Ryszard Pisarski. They played instrumental music influenced by hard rock bands, mainly Deep Purple, Led Zeppelin and Black Sabbath. In 1981, during the first edition of the Silesian Rock festival, the band found a vocalist, Roman Kostrzewski. The line-up was filled out by guitarist Wojciech Mrowiec and in 1984 Kat released the debut single "Noce szatana / Ostatni tabor" (Polish for The Nights of Satan / The Last Train). Robert "Lor" Milewski authored the lyrics of both songs, however since then Kostrzewski became the lyricist (until his departure), which added to bands' popularity, because of his unique writing style, incorporating poetry, Polish folklor and mysticism. While playing at Jarocin Festival, band met with listeners' enthusiasm, although the first accusation of promoting satanism also appeared. Allegations turned up due to the behaviour of another band, Kreon (formerly Test Fobii) which broke a Christian cross and then celebrated a Black Mass. The band also toured with Hanoi Rocks.
In 1985 Kat released their debut album Metal & Hell. A Polish language version of this full-length was released as a limited album in the same year, but title was changed to 666. Soon after, Wojciech Mrowiec quit the band. In 1987 Kat performed twice as a support band for Metallica in Katowice's Spodek. This show was documented in Kat's live album 38 Minutes of Life. At that time they also supported Running Wild, Helloween and Overkill.
After releasing the next full-length album, Oddech wymarłych światów, band had an internal crisis and, as a result, broke up. It began with a conflict with band's manager, Tomasz Dziubiński. Finally, Kat reformed in 1990 and in 1992 played with TSA and Acid Drinkers during Jarocin Festival. Two years later, some songs from this show appeared along their new ones on a new album, Bastard (1992). The album consisting of nine highly-technical thrash metal pieces with extraordinary lyrics (this time with visible influences of Polish poet Tadeusz Miciński ) is considered among the greatest of Polish metal records.
In 1994 in Wisła a new album entitled Ballady was compiled and recorded. It includes Kat's ballads from previous albums, previously unreleased tracks and two completely new songs. Józef Skrzek was a guest keyboard instrumentalist. In that year, Metal Mind Productions re-released the three first of Kat's albums without the band's permission. Kat sued the company and, after a few years, won the case.
In 1996 and 1997, Kat released the albums Róże miłości najchętniej przyjmują się na grobach (a big success in Poland) and Szydercze zwierciadło (during its recording Piotr Luczyk temporarily left the band). After Jacek Regulski died in a motorcycle accident in 1999, the band split up for three years. They returned in 2002 and held a tour called "On Tour Again", again with Luczyk on guitar. They also played as a support before Iron Maiden during Mystic Festival in Hala Ludowa, Wrocław, 2002. During that period they were occasionally supported live by Polish guitarist Valdi Moder.
In 2004 and 2005 Kat had several important changes in its line-up. Firstly, band fired the drummer, Ireneusz Loth and then, vocalist and lyricist Roman Kostrzewski. Mariusz Prętkiewicz replaced the former drummer. Jarosław Gronowski joined as a second guitarist and Henry Beck became a new vocalist. Gronowski played in Kat during the Szydercze zwierciadło promotional tour (since Luczyk was at the time out of the band). Reformed band released an album Mind Cannibals in 2005. It's the second English language album of Kat (after first LP, Metal & Hell). The lineup changes were very controversial, and band's fan base actually split in two, because Roman Kostrzewski and Ireneusz Loth also created their own band (under monicker "Kat & Roman Kostrzewski") and continue to perform since then.
After recording "Mind Cannibals", the band went on tour around Europe (playing together with, for example, Six Feet Under), but no concert took place in Poland. This added to the controversy (Kostrzewski and Loth were at the time very active with their new band). Some Polish fans believed that Kat wouldn't play in Poland at all - because of "Mind Cannibal's"' mixed reception in Poland and the fact that former vocalist, Kostrzewski, is extremely popular in their homeland - and in fact, they haven't played in Poland since 2005.
Since 2005, Kat went on hiatus, although there are rumours about possible succesor to "Mind Cannibals" in Polish press.