The distribution of the leptin receptor in the brain of C57 mice was investigated using a non-radioactive in situ hybridization method. Leptin receptor mRNA expression was highest in the arcuate nucleus and median eminence of the hypothalamus, but it was also abundant in hippocampus, primarily in the dentate gyrus and CA1, and was detected at low levels in piriform cortex and the medial margin of the medial habenular nucleus. The localization of leptin receptor-containing neurones in the present study indicates the possibility that the leptin receptor is expressed on neuropeptide Y-containing neurones.