BST-1 is an ectoenzyme expressed on human bone marrow. Stromal cells and myeloid lineage cells, having both ADP-ribosyl cyclase and cyclic ADP-ribose (cADPR) hydrolase activities. In mouse, BST-1 is also expressed on lymphoid progenitors. We isolated chromosomal DNA segments of the human BST-1 gene. The human BST-1 gene consisted of nine exons and eight introns. The length of each exon was very similar to that of the Aplysia ADP-ribosyl cyclase gene. The flanking region of the BST-1 gene contained several potential binding sites for nuclear factors, NF-kappa B, p53, NF-IL6, CREB, PEA3, E2A, C/EBP, AP3, AP2 and SP1 and consensus sequences for gamma-IRE and ISRE like element. Copyright (C) 1996 Elsevier Science B.V.