Research in renal physiology began later in the USA than in Europe. Initial studies in the early 1900s dealt with the pathophysiology of renal failure. Micropuncture study of single nephron function was initiated in the laboratory of A.N. Richards in the early 1920s and with the later addition of microperfusion provided important insights into the site and mechanisms of solute transport. In parallel, with the leadership of Homer Smith, the development of noninvasive clearance methods to measure glomerular filtration rate and renal blood flow initiated a fruitful period of quantification of renal hemodynamics and of transport by the tubules. The steady progress of renal physiology in the USA owes much to the generous support of basic reasearch by the National Institutes of Health. It is also worthy of mention that progress in renal physiology in the US owes much to work carried out in clinical departments and to the type of comparative studies exemplified by work at the Mt. Desert Island Biological Laboratory.