The 2002 Summer School on Astroparticle Physics and Cosmology was held at ICTP, in the three weeks from June 17 to July 5. As in previous Schools in this series, the main topics were covered by sets of 3-5 lectures (regular courses); some special topics were presented in dedicated sessions (special lectures); and emphasis was given to the discussion sessions. We were greatly pleased - and to some extent surprised - that most lecturers agreed to give lectures at the blackboard, thus giving a chance even to newcomers to follow the details of the derivations and not only the main arguments. We were even more pleased by the atmosphere of the School, conducive to discussions and to intellectual exchange, and by the support of the good summer weather in Trieste. The main aim of the School was to give an updated survey of astroparticle physics and cosmology, with an emphasis on theoretical aspects. W. Hu introduced and discussed the theory of structure formation, and the most important features of the cosmic microwave background radiation (interest in which has been further boosted after WMAP). A closely connected topic, inflation, was reviewed in detail in the lectures of A. Riotto. The connection between dark matter and particle physics was outlined by R. Bernabei (whose experiment, DAMA, recently obtained a strong evidence for a WIMP-like candidate). The search for other dark matter candidates, such as monopoles and axions, was discussed by G. Giacomelli and E. Massò. Dark energy and the cosmological constant - the most puzzling aspect of particle and astroparticle physics, according to many - were the topics of the lectures of G. Dvali, who offered many stimulating proposals and speculations. G. Gabadadze reviewed the physics of large extra dimensions, and suggested a number of applications of these ideas in cosmology. Field theory at finite temperature has been presented by M. Laine. S. Sarkar and P. Tinyakov addressed the cosmic rays of ultra-high energies and discussed the puzzles they pose to astrophysics and particle physics. The lectures of W. Buchmüller provided an overview of current ideas about baryogenesis, and in particular the mechanism of leptogenesis - which draws a connection with neutrino masses. A.Yu. Smirnov discussed the status of the solar neutrino problem (which, after SNO and KamLAND experiments, is in practice solved and shows the correctness of MSW theory). An introduction to neutrino astronomy was given by F. Vissani. Finally, L. Rezzolla gave a detailed discussion of the status and perspectives for gravitational wave detection (of great interest for interferometers like VIRGO and LISA coming to operation) and of the most likely astrophysical targets for this search, such as black holes or neutron stars. (ISBN 92-95003-20-9)