Objective: To verify whether there exists melatoni n(Mel) receptor in human embryonic nervous system. Methods: Spec ific binding of Mel to embryonic brain and spinal cord was measured by radioliga nd binding assay. Results: 125　I-Mel binding s ites in optomeninx was the most, in eptochiasm and sniff ball was next; GTPγS d ose-de pendently inhibited the binding. Conclusion: The results demonst rate the presence of specific binding of Mel in human embryonic brain and spinal cord. GTPγS has some effect on 125　I-Mel specific binding,support ing the theory that Mel receptor is coupled to inhibitory G-proteins.