The Robert F. Pitts Memorial Lectureships were founded in 1978, when the many friends and admirers of Robert Pitts established a fund in memory of that distinguished physiologist. The lecturer is selected by the Renal Commission of the International Union of Physiological Sciences, with the Chair of Physiology at Cornell University Medical College acting ex officio. The lecture is presented at each International Congress of Physiological Sciences. At the XXXth Congress held in Vancouver, Canada, the Pitts Lecturer was Professor Gerhard Malnic from Sao Paulo, Brazil. He delivered the lecture on July 15, 1986. There are several aspects about the choice of Professor Malnic that seem singularly fitting. First and foremost, he is an outstanding physiologist who, like Robert Pitts, has contributed much to our understanding of renal function. Of Pitts' many contributions to physiology, the major one was probably his brilliant elucidation of how the kidney maintains hydrogen ion balance, and it is in this area that Gerhard Malnic has done most of his original work. Professor Malnic received his major postdoctoral training in Dr. Pitts' department at Cornell. There, under the tutelage of Gerhard Giebisch, Professor Malnic became first author on a series of three classic papers, published in 1964 and 1966, which conclusively showed, by micropuncture techniques, how the kidney handles potassium. And it was again at Cornell, in a later sojourn as Visiting Scientist, that Professor Malnic began his long and fruitful studies on the renal handling of hydrogen ion. Gerhard Malnic was born in Italy, of Austrian parents. In 1956, he became a citizen of Brazil, where he received his medical training. In the intervening thirty years, he has become a leader in South American physiology and science. He has served as Secretary–General of the Latin American Association of Physiological Sciences and as President of the Brazilian Physiological Society, and he is a member of the Academies of Sciences of both Brazil and Latin America. Currently, he holds the position of Professor and Chair of the Department of Physiology and Biophysics at the University of Sao Paulo. Professor Malnic's work on the renal handling of hydrogen ion has progressed from a methodical description of acidification along the nephron to exploring the detailed mechanisms that govern the tubular secretion of hydrogen ion. It is the latter aspect that formed the major topic of his Robert F. Pitts Lecture. Heinz Valtin Chair, Renal Commission Previous Robert F. Pitts Memorial Lecturers, 1980 Rolf Kinne, Federal Republic of Germany, 1983 James A. Schafer, U.S.A.