The full-length cDNA encoding the human calbindin-D9k (CaBP-9k) has been cloned using reverse transcription/PCR methodology with rat- and bovine-derived primers and intestinal RNA. A core product, and both a 5' and 3' product encompassing the full-length cDNA were obtained. The clones include coding region for 79 amino acids, 57 nucleotides 5'-and 159 nucleotides 3'-non-coding region, and a poly(A) tail. The deduced protein sequence is homologous to other mammalian CaBPs. Northern analysis revealed the mRNA in human duodenum to be about 600 nucleotides in length. Expression levels in adult human tissue were substantially lower than in child, rat or porcine intestine.