Information on the genetics and metabolism of 4-aminobutyrate (GABA) in yeasts and fungi is reviewed. In spite of ubiquitous occurrence, there is limited information on its function and biological role. Most fungi utilize GABA both as a carbon and a nitrogen source. Fungal endogenous GABA largely originates from the decarboxylation of L-glutamate and is associated with sporulation/spore metabolism. Whatever its source, GABA is catabolized to succinate via succinicsemialdehyde. Taken together these steps define a potential bypass outside the classical tricarboxylic acid cycle. Evidence for the existence of such a functional bypass in fungi is reviewed. The role of GABA and its metabolism in various facets of fungal biology is gradually emerging.