In 1959 and 1960 the Pan American Health Organization sponsored conferences to consider the problems of live poliovirus vaccines. The success stimulated by these no doubt prompted the recent meeting on the broader topic of vaccines against viral and rickettsial diseases. The present volume presents a potpourri of excellent papers and discussions on the ever-increasing production and evaluation of vaccines to control a variety of agents. The sessions reported cover current aspects of control of acute respiratory diseases; enteroviruses; arboviruses and herpesvirus group; exanthems and mumps; smallpox, rabies, and hepatitis; ricksettsiae, Bedsoniae; adjuvants; and vaccination problems. Other approaches to the control of viral diseases are reviewed, such as the newer areas of chemoprophylaxis and the potential use of induced interferons. These topics, while extending beyond the title, are quite properly included as frontier areas, that in time may be appropriate mechanisms of control.