Since 1975, Marcel Grossmann meetings have been organized to provide opportunities for discussing advances in gravitation, general relativity and relativistic field theories, emphasizing mathematical foundations, physical predictions and experimental tests. The object of these meetings is to facilitate exchange among scientists that may deepen our understanding of space-time structures and to review the status of ongoing experiments aimed at testing Einstein's theory of gravitation from either the ground, or space. The 8th meeting took place in June 1997 and the scientific programme included...