It is proposed that CMAP (leukocystatin/cystatin F, HGMW-approved symbol CST7) expression is correlated with the metastatic potential of malignant tumors. FISH analysis of human and murine CMAP revealed the genomic loci 20p11.21-p11.22 of the human family 2 cystatin cluster and mouse chromosome region 2G1-G3, respectively. Like murine CMAP, the human CMAP gene is constructed from four divided exons, all of which encode the functional domains of the putative translational product. Based on the computational analysis, a novel gene weakly similar to the plant strictosidine synthase, named BSCv (HGMW-approved symbol C20orf3), was identified on the opposite allele at a distance of a few kilobases from the human CMAP gene. In between human CMAP and the BSCv gene, there is a unique tandem repeat sequence. CpG-rich island characteristics and GC-box features normally observed in housekeeping genes were not seen around exon 1 of the CMAP gene, reflecting the restricted expression of CMAP in hematopoietic cells.