Abstract: In order to find the morphological evidence that leptin plays a role in control of reproductive endocrine in the level of the hypothalamus, coexistence of OB-Rb mRNA and LHRH-like immunoreactive (LHRH-IR) in neurons of the pig forebrain was studied by combination of in situ hybridization and immunohistochemistry methods. The results showed that both OB-Rb mRNA and LHRH-IR containing neurons(dual labelled neurons) were seen in the hypothalamus, hippocampal formation, amygdala and cerebral cortex of the pig, and that some neurons expressing OB-Rb mRNA also contained LHRH-IR. It meant coexistence of OB-Rb mRNA and LHRH-IR in these neurons of the pig forebrain. In the hypothalamus, dual labeled neurons were seen in the paraventricular nucleus, periventricular nucleus, ventromedial nucleus, lateral area and arcuate nucleus. In the hippocampal formation, dual labeled neurons were mainly found in the polymorphic layer and the granular layer of the dentate gyrus and in the pyramidal layer of the hippocampus. In the cerebral cortex , dual labeled neurons were mainly observed in the Ⅲ~Ⅴlayers. The results suggested that leptin probably regulate endocrine and reproduction of animal through directly imposing on the GnRH neurons expressing OB-Rb in the hypothalamus.