The hASNA-I is a novel human arsenite-stimulated ATPase identified as the human paralogue of the ATPase component of the arsenite efflux system in E. coli. The hASNA-I has distinct biochemical properties and a dual nuclear and cytoplasmic distribution. Immunohistochemical staining showed a distinct pattern of hASNA-I expression in cells within normal tissues, and its overexpression in breast cancer. Recently, the yeast two-hybrid system has identified hASNA-I as a cellular partner of metallothionein II suggesting an additional role in Zn homeostasis and cellular detoxification. This report describes the assignment of hASNA-I to human chromosome 19 by somatic-cell hybrid PCR mapping, the isolation of a chromosome 19-specific cosmid clone, and the genomic structure and exon-intron boundaries of hASNA-I. Our results indicate that the coding region of hASNA-I consists of 4 exons spanning 6 kb on band 19q13.3. These data will facilitate molecular analysis of the role of hASNA-I in human disease.