The fifty-seven papers presented in this volume give a complete overview of the knowledge to date in radiation biology. The accessibility of the unique radiation environment in space and the increasing involvement of human beings in space missions have initiated substantial research activities in the various fields of space radiation biology dealing with radiation detection and measurement; biological mechanisms of the hard component of cosmic radiation; impact of space environment on radiobiological processes and also radiation protection issues. Besides offering opportunities for radiobiological experiments in space, the current space exploration programme even requires the collection of radiobiological data in space and at accelerators as baseline information for estimating radiation risks to humans on future space missions and for establishing radiation standards for manned spaceflight.