A cDNA for pig phosphoglucose isomerase (PGI) was used to isolate genomic clones representing the 5' portion of the corresponding gene. A total of 656 bases of the pig PGI gene were obtained that include 5'-flanking information and part of exon 1. A major transcription start was localized at 74 nucleotides from the translation start. The sequence organization of the pig PGI promoter is similar to that of other housekeeping genes. This GC-rich region includes a TATA-like box, two putative Sp1 recognition sites but no CCAAT box.