Reprinted from 
Proc. Nat. Acad. Sci. USA 
Vol. 72, No. 6, pp. 1981-1984, June 1975 
Summary Statement of the Asilomar Conference on Recombinant DNA 
Molecules* 
PAUL BERGf, DAVID BALTIMORE}, SYDNEY BRENNER§, RICHARD 0. ROBLIN 111% AND 
MAXINE F. SINGER|| 
Organizing Committee for the International Conference on Recombinant DNA Molecules, Assembly of Life Sciences, National Research 
Council, National Academy of Sciences, Washington, D.C. 20418. f Chairman of the committee and Professor of Biochemistry, 
Department of Biochemistry, Stanford University Medical Center, Stanford, California; t American Cancer Society Professor of Micro- 
biology, Center for Cancer Research, Massachusetts Institute of Technology, Cambridge, Mass.; § Member, Scientific Staff of the Medical 
Research Council of the United Kingdom, Cambridge, England; H Professor of Microbiology and Molecular Genetics, Harvard Medical 
School, and Assistant Bacteriologist, Infectious Disease Unit, Massachusetts General Hospital, Boston, Mass.; and || Head, Nucleic Acid 
Enzymology Section, Laboratory of Biochemistry, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 
I. INTRODUCTION AND GENERAL CONCLUSIONS 
This meeting was organized to review scientific progress in 
research on recombinant DNA molecules and to discuss 
appropriate ways to deal with the potential biohazards of this 
work. Impressive scientific achievements have already been 
made in this field and these techniques have a remarkable 
potential for furthering our understanding of fundamental 
biochemical processes in pro- and eukaryotic cells. The use of 
recombinant DNA methodology promises to revolutionize the 
practice of molecular biology. Although there has as yet been 
no practical application of the new techniques, there is every 
reason to believe that they will have significant practical 
utility in the future. 
Of particular concern to the participants at the meeting 
was the issue of whether the pause in certain aspects of 
research in this area, called for by the Committee on Re- 
combinant DNA Molecules of the National Academy of 
Sciences, U.S.A. in the letter published in July, 1974** 
should end; and, if so, how the scientific work could be under- 
taken with minimal risks to workers in laboratories, to the 
public at large, and to the animal and plant species sharing 
our ecosystems. 
The new techniques, which permit combination of genetic 
information from very different organisms, place us in an 
area of biology with many unknowns. Even in the present, 
more limited conduct of research in this field, the evaluation 
of potential biohazards has proved to be extremely difficult. 
It is this ignorance that has compelled us to conclude that it 
would be wise to exercise considerable caution in performing 
this research. Nevertheless, the participants at the Conference 
agreed that most of the work on construction of recombinant 
DNA molecules should proceed provided that appropriate 
safeguards, principally biological and physical barriers ade- 
* Summary statement of the report submitted to the Assembly of 
Life Sciences of the National Academy of Sciences and approved 
by its Executive Committee on 20 May 1975. 
Requests for reprints should be addressed to; Division of Medical 
Sciences, Assembly of Life Sciences, National Academy of 
Sciences, 2101 Constitution Avenue, N.W., Washington, D.C. 
20418. 
** Report of Committee on Recombinant DNA Molecules; 
“Potential Biohazards of Recombinant DNA Molecules,” Proc. 
Nat. Acad. Sci. USA 71, 2593-2594, 1974. 
quate to contain the newly created organisms, are employed. 
Moreover, the standards of protection should be greater at 
the beginning and modified as improvements in the method- 
ology occur and assessments of the risks change. Furthermore, 
it was agreed that there are certain experiments in which the 
potential risks are of such a serious nature that they ought 
not to be done with presently available containment facilities. 
In the longer term, serious problems may arise in the large 
scale application of this methodology in industry, medicine, 
and agriculture. But it was also recognized that future re- 
search and experience may show that many of the potential 
biohazards are less serious and/or less probable than we now 
suspect. 
II. PRINCIPLES GUIDING THE RECOMMENDATIONS 
AND CONCLUSIONS 
Although our assessments of the risks involved with each of 
the various lines of research on recombinant DNA molecules 
may differ, few, if any, believe that this methodology is free 
from any risk. Reasonable principles for dealing with these 
potential risks are: (i) that containment be made an essential 
consideration in the experimental design and, (ii) that the 
effectiveness of the containment should match, as closely as 
possible, the estimated risk. Consequently, whatever scale of 
risks is agreed upon, there should be a commensurate scale of 
containment. Estimating the risks will be difficult and in- 
tuitive at first but this will improve as we acquire additional 
knowledge; at each stage we shall have to match the potential 
risk with an appropriate level of containment. Experiments 
requiring large scale operations would seem to be riskier than 
equivalent experiments done on a small scale and, therefore, 
require more stringent containment procedures. The use of 
cloning vehicles or vectors (plasmids, phages) and bacterial 
hosts with a restricted capacity to multiply outside of the 
laboratory would reduce the potential biohazard of a par- 
ticular experiment. Thus, the ways in which potential bio- 
hazards and different levels of containment are matched may 
vary from time to time, particularly as the containment 
technology is improved. The means for assessing and balanc- 
ing risks with appropriate levels of containment will need to 
be reexamined from time to time. Hopefully, through both 
formal and informal channels of information within and be- 
tween the nations of the world, the way in which potential 
biohazards and levels of containment are matched would be 
consistent. 
1981 
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