Acid trance is a style of trance music that emerged in the late 1980s and early 1990s focusing on utilising the acid sound. The trademark sound of "acid" is produced with a Roland TB-303 by playing a sequenced melody while altering the instrument's filter cutoff frequency, resonance, envelope modulation, and accent controls. This real-time tone adjustment was not part of the instrument's original intended operation. Acid trance is the best known form of trance music in Belgium. The form was first showcased at the popular Antwerp Rave 24 in Belgium, and has created four national number one singles in the country since.

Acid trance may be considered a descendant of acid house, since the genre of trance had not yet been invented during the advent of acid house (or acidhouse).

The first volumes of Trancemaster compilations contains a few tracks in acid trance style, just as classic trance tracks. The difference is, while acid trance tracks focus more on the changing TB-303 lines, classic trance (e.g. Dance 2 Trance, Cosmic Baby, Age of Love & Jam & Spoon) tracks are more atmospheric, they use "softer" synth-lines, often stings and other ambient music elements. The line between these two styles is quite blurred; they also emerged about the same time.

Kai Tracid (born as Kai Franz on 17 January 1972 in Hanover, Germany) is a German Trance DJ and producer. The name Tracid originates from the combination of the two music genres trance and acid.

In Germany he became famous with his first single, "Your Own Reality". In 1998 he gained world-wide fame with Liquid Skies. In November 2001 he got his first Top-10 hit in the German single charts. Since 2000 he releases his records under his own record company Tracid Traxxx.