Calf prochymosin (cPC) gene was cloned from calf abomasum DNA by using a cloned cPC cDNA as a probe. The cPC gene spans approx. 10.5 kb and consists of 9 exons and 8 introns. The positions of exon-intron junctions coincide completely with those in the human pepsinogen gene. Analysis of 5'-flanking region sequence and S1 nuclease mapping revealed that the transcriptional start point was located 25 bp upstream from the start codon and that the putative transcriptional promoter sequences (TATA box and CCAAT box) were located in -30 and -90 regions, respectively. Some distinctive sequences possibly functioning as regulatory signals for gene expression are present at the 5'-flanking region.