A contiguous region of cellular DNA sequence, 64 kb in length and representing overlapping cellular inserts from three independent cosmid clones, has been isolated from a representative library of human lung carcinoma DNA partially digested with MboI. Within this region of the cellular genome, v-abl homologous sequences are dispersed over a total region of around 32 kb. These sequences represent the entire v-abl human cellular homologue, are colinear with the viral v-abl transforming gene, and contain a minimum of seven intervening sequences. At least eight regions of highly repetitive DNA sequences have been shown to map in close proximity to c-abl coding sequences. In addition to the major c-abl human locus, three regions of human DNA sequence, corresponding to only portions of the v-abl gene, have been identified. Two of these have been molecularly cloned and shown to be distinct from the primary human c-abl locus. Upon transfection to rat embryo fibroblasts in culture, none of the cosmid DNAs containing v-abl homologous sequences exhibited transforming activity. These findings identify and map a single genetic locus of human DNA, c-abl, representing the complete v-abl homologue, and demonstrate the existence of additional human DNA sequences corresponding to more limited, subgenomic regions of v-abl.