Experimental and occupational exposure to methyl tert-butyl ether (MTBE) has been reported to induce neurotoxicological and neurobehavioral effects, such as headache, nausea, dizziness, and disorientation, etc. However, the molecular mechanisms involved in MTBE-induced neurotoxicity are still not well understood. In the present study, we investigated the effects of MTBE on spatial memory and the expression and function of GABA(A) receptor in the hippocampus. Our results demonstrated that intraventricular injection of MTBE impaired the performance of the rats in a Morris water maze task, and significantly increased the expression of GABA(A) receptor alpha1 subunit in the hippocampus. The phosphorylation of ERK1/2 decreased after the MTBE injection. Furthermore, the decreased ability of learning and the reduction of phosphorylated ERK1/2 level of the MTBE-treated rats was partly reversed by bicuculline injected 30 min before the training. These results suggested that MTBE exposure could result in impaired spatial memory. GABA(A) receptor may play an important role in the MTBE-induced impairment of learning and memory by regulating the phosphorylation of ERK in the hippocampus.