In the last few decades biology has made extraordinary progress in all its domains. Some of this progress, as in human genetics or immunology, is especially interesting for human life. Another part has had an impact in the field of agriculture and in industry. As a result, humankind is looking forward to biotechnology as a solution to many problems of welfare, protection of natural resources, energy, etc. Important progress has been made in the concepts and techniques related to the work done on nucleic acids and on recombinant DNA. At the same time the development of techniques such as cloning and tissue culture has increased the prospects of biomedical research. However, our high hopes in modern biology are counterbalanced by our apprehensions regarding its possible misuse. This was why the Pontifical Academy of Sciences chose “Modern Biological Experimentation” as the theme of a Study Week. It is clear that biological experimentation involves some moral problems which are outside the realm of science proper. The Pontifical Academy of Sciences, being a science academy, has treated the theme in scientific terms. However, deep down the misuse of modern biology is a constant preoccupation. The benefits of modern biology are dependent on the understanding that human life and dignity have to be protected.