Human DNA coding for renin was identified and sequenced. The gene consisted of 10 exons corresponding to a 1500 nucleotide mRNA was broken up by long stretches of 'nonsense' DNA (introns) and spanned 12,000 base pairs. In addition, the sequence of nucleotides involved in regulation of the gene was determined by sequencing upstream. Prediction of the amino acid sequence of human preprorenin revealed likely sites of processing. This helps explain many past experimental observations. For example, the pro region contained adjacent likely cleavage sites for trypsin and pepsin and so reveals why both trypsin and pepsin can activate prorenin. The structure of human renin had features involved in its highly specific hydrolysis of the Leu10-Val11 bond unique to human angiotensinogen: in particular leucine 224 (instead of valine). Renin gene expression was studied in the mouse by quantification of both renin activity and its mRNA. Sodium depletion, captopril and spironolactone increased expression of Ren-1 in the kidney. The unusual, duplicated, mouse gene, Ren-2, which is expressed in the submandibular gland was, regulated by (dihydro)testosterone in male mice and by thyroid hormone in female mice.