science in Latin America. The early publication of this symposium has been made possible through the efforts of an editorial board consisting of Dr. F. T. Kenney (Oak Ridge National Laboratory), Dr. Gabriel Favelukes (University of La Plata), Dr. Barbara Ham­ kalo (Oak Ridge National Laboratory), and Dr. J. T. August (Albert Einstein College of Medicine). As in previous symposia, excellent support has come from the Ford Founda­ tion through a grant to the National Academy of Sciences, the United States Atomic Energy Commission, the National Science Foundation, OAS, and other groups. Through the cooperation of the authorities at the University of La Plata, the Albert Einstein College of Medicine (the United States cosponsoring university), and other schools, this very successful symposium was made possible.