Gamma-aminobutyric acid is a major inhibitory neurotransmitter in the central nervous system. GABA metabolism is dependent on the activity of three enzymes: glutamic acid decarboxylase, GABA-transaminase and succinic semialdehyde dehydrogenase. Decreased activity of these enzymes may cause many neurological syndromes, such as stiff-person syndrome, chronic fatigue syndrome, anxiety disorders and seizures. This article is a review of most important problems related to an impairment of GABA metabolism.