In July 14-30, 1999 an Italian scientific expedition was carried out in Tunguska (Siberia), the region of the 1908 explosion of a cosmic body (see Di Martino, M. et al., 1998, and references therein). The expedition, named "Tunguska99", was organized by the Department of Physics of the University of Bologna, in collaboration with the Turin Astronomical Observatory and the Institute of Marine Geology (CNR Bologna) and with the local support of personnel and researchers of Tomsk University (Russia). The "Tunguska99" expedition is a contribution to the international programs on the detection and physical study of asteroids and comets potentially dangerous to humankind.