GABA(A) receptors are the major inhibitory neurotransmitter receptors in the mammalian brain, implicated in anxiety, depression, epilepsy, insomnia, and learning and memory. Here, we present several lines of evidence for involvement of the GABAergic system, and in particular the GABA(A) receptor-mediated function, in fragile X syndrome, the most common form of inherited mental retardation. We argue that an altered expression of the GABA(A) receptor has neurophysiologic and functional consequences that might relate to the behavioural and neurological phenotype associated with fragile X syndrome. Interestingly, some neuropsychiatric disorders, such as anxiety, epilepsy and sleep disorders, are effectively treated with therapeutic agents that act on the GABA(A) receptor. Therefore, the GABA(A) receptor might be a novel therapeutic target for fragile X syndrome.