None of man's achievements is more remarkable than his recently won capacity to be exposed to, and return successfully fram, pressures of more than sixty times the Earth's atmospheric pressure, 610 m below the surface of the sea. But raised environmental pressure is also a tool that is not sufficiently used in biomedica I research. While knowledge of the effects of such pressure upon man is important for the success and safety of deepsea diving, the effects of pressure upon molecular and cellular mechanisms illuminate some of the more fundamental life processes and raise wider implications. This book reports the Discussion Meeting of the Royal Society at which academic, naval and industriai research workers brought together these many aspects of raised environmental pressure and reviewed recent developments. It will be of value and interest to researchers in most basic and applied biological and medicai sciences, as well as to the amateur diver.