We describe a 17-year-old girl with Kleine-Levin syndrome (KLS), in which gabapentin was effective for the prevention of attacks. (99)mTc-ECD SPECT revealed hyperperfusion of the thalamus and nucleus accumbens presenting in the symptomatic period, suggesting epilepsy-like neuronal discharge from these structures. Treatment for KLS has not been established, although lithium has been used in limited cases with insignificant efficacy. Here, we report a case of recurrent hypersomnia in which gabapentin was effective for the prevention of attacks. We speculate that the recurrent hypersomnia and behaviour disturbance are related to epilepsy-like neuronal discharge from the thalamus due to dysfunction in GABAnergic receptors.