Transgenic mice were used to locate the cis-acting DNA elements that are important for efficient, tissue-specific expression of the mouse albumin gene in the adult. Chimeric genes with up to 12 kb of mouse albumin 5'-flanking region fused to a human growth hormone (hGH) reporter gene were tested. Remarkably, a region located 8.5-10.4 kb upstream of the albumin promoter was essential for high-level expression in adult liver and the region in between -8.5 and -0.3 kb was dispensable. The far-upstream region behaved like an enhancer in that its position and orientation relative to the albumin promoter were not critical; however, it did not function well with a heterologous promoter. Two of four DNase hypersensitive sites found in the 5'-flanking region of the albumin gene map to the far-upstream and promoter regions; the others may reflect regions involved in developmental or environmental control of this gene.