MY first choice of a subject for the Cutter Lecture on Preventive Medicine was naturally something from my own primary field of interest, viral disease. There was a disadvantage, however, that work on the public-health side of viral disease has become of rather minor interest in my own laboratory and not much that is new can be reported on our main topic of Murray Valley encephalitis.For the last two years, however, I have had to undertake the responsibility of acting as chairman to the Australian Government's National Radiation Advisory Committee, which is concerned with advising on the medical hazards . . .