The neuropeptide Orexin is involved in the regulation of the sleep-awake cycle and feeding behavior. We isolated a 22-kb genomic clone containing the 5' flanking region of the mouse Orexin promoter. We determined that the transcription start site (+1) is located 96 nucleotides upstream of the initiation codon. The start site region contained consensus sequences corresponding to the transcription initiator and TATA box. Analysis of promoter activity using PC12 cells showed that regions between -13 and +112 and between -1,868 and -780 contained nerve growth factor (NGF)-responsive positive regulatory element and a negative regulatory element respectively.