This chapter on new methods of molecular biology applied to the investigation of the renin-angiotensin system (RAS) contains a description of a clinical case in its first section. There are two reasons for this. First, the case will illustrate the importance of increased understanding of the RAS, because of research by basic scientists, for clinical scientists, clinicians, and human health. Second, and more importantly, describing the applicability of scientific advances in the understanding of RAS to a particular patient is a fitting tribute to two remarkable clinician scientists, Irvin Page and Eduardo Braun Menendez, the co-discoverers of angiotensin II (Ang II) in the United States and Argentina, respectively (1,3). Their insurmountable curiosity was driven by a desire to help patients, at a time at which human hypertension was an untreatable and devastating problem.