We cloned genomic DNA fragments containing the ABO gene in 1995. The gene spans more than 18 kilobases, and the coding sequence scatters over 7 exons, with the longest coding sequence in the last exon. We determined the exon-intron boundaries, and found that they all follow the GT-AG splicing rule. The 3’ untranslated region is rich with repeat sequences, and may be involved in the stability of the messages. We also delineated the promoter region of the ABO gene. Kominato played the major role in the promoter characterization. To do so, we constructed a luciferase reporter construct with the potential promoter region of the ABO gene that precedes the transcription initiation codon, as well as different sizes of nested deletion. We determined the promoter activity of the constructs and located the region with the promoter activity. The promoter is rich with CG, and there is an enhancer element further upstream.