Major changes have occurred in the field of brachytherapy during the last twenty years. A symposium would serve to review the present status, to emphasize the progress, and to determine future directions. The fact that Memorial Hospital develops many traditional and most modern techniques of brachytherapy makes it the natural place to hold the symposium. The first radioactive encapsulated radon sources for brachytherapy were developed and used clinically here around 1910. Development of atomic reactors introduced artificial radioactive sources into medicine. In 1955 Memorial Hospital pioneered the clinical use of Iridium 192 sources. Simultaneously, a technique of manual afterloading was developed here by Dr. Ulrich K. Henschke. Both afterloading of radioactive sources and the low energy iodine 125 seeds, introduced in 1965 and applied clinically first at Memorial Hospital, has eliminated the problem of radiation exposure to medical and paramedical personnel. Remote afterloading of intracavitary applicators employing moving high energy cobalt sources was developed here and used clinically since 1967. Finally, Memorial Hospital is first to begin a controlled clinical study of Cf-252, most recent of the artificial encapsulated radioactive sources.