Adiponectin, a cytokine hormone secreted exclusively by adipose tissue, has key roles in energy homeostasis, and in glucose and lipid metabolism. To understand the regulatory expression of pig adiponectin, the 5'-flanking region of the adiponectin gene was isolated from a pig BAC library. 5'-RACE analysis revealed that there were three transcriptional start sites, including one that is novel. The luciferase reporter assay detected a positive cis-acting element for efficient expression of the adiponectin gene at the region spanned by nucleotides -1150 to -1130 with serially deleted 5'-flanking sequences as its promoters. Analysis of oligonucleotide competition by the electrophoretic mobility-shift assay revealed the presence of a cAMP-responsive element (CRE) (nucleotides -1150 to -1130) for the cAMP-responsive element binding protein (CREB), which has not been reported in human or mouse adiponectin genes. These results indicated that CREB is an essential regulatory factor for the transcriptional activity of pig adiponectin.