I 
STANFORD UNIVERSITY MEDICAL CENTER 
STANFORD, CALIFORNIA 94305 
DEPARTMENT OF BIOCHEMISTRY PAUL BERG 
Willson Professor of Biochemu- 
September 20, 1978 
Dr. Donald Fredrickson, Director 
National Institute of Health 
Building 1, Room 124 
Bethesda, Maryland 20014 
Dear Don, 
Your commentary and the proposed revisions of the Recombinant 
DNA Guidelines revealed how far we have moved since the issue of 
potential risks associated with recombinant DNA research was 
first raised publicly. In spite of the occasional ferocity, 
stridency and all too frequent politicalization of the discussions, 
features that turned me and others off to continuing involvement, 
you and your colleagues have persevered, steered a reasonable 
course while peppered with foolish and intemperate advice and 
arrived at proposals, which in the main are workable and a basis 
for further evaluation. 
My estimate of the potential risks of recombinant DNA 
research and how to deal with them have certainly changed in the 
last few years. There is nothing remarkable or sinister about 
that; as scientists we are obliged, constantly, to reexamine and 
reinterpret our hypotheses, taking into account new developments, 
new data and fresh insights. The Asilomar Converence Report 
insisted repeatedly that the premises, conclusions and practices 
in the recombinant DNA field needed to be reviewed, reevaluated 
and updated continuously. Lest there be any misunderstanding 
about how I feel now let me say that I no longer have concerns 
about the safety of most recombinant DNA experimentation; 
consequently, it becomes increasingly difficult to justify to 
myself and others the amount of time and money being expended 
against risks that are highly improbable: perhaps more 
unlikely than the probability that space vehicles reentering 
our atmosphere will fall in populated areas (a possibility which 
elicited little concern or comment from the media or public 
spirited citizens) or any one of hundreds of other potentially 
calamitous but routine activities and practices. I could be 
mistaken in my estimate of the risks but I don't believe so. 
However, being fallible, I have supported the NIH's efforts to 
devise sensible and workable guidelines to minimize the possibility 
of any risk. I can continue to do so as long as they do not 
become unnecessarily restrictive and stifling to research progress 
[A-208] 
