The chemical processes of formation and destruction of molecules have been found to be widespread in astronomical scenario. It occurs in comets, planetary atmospheres including ionospheres, early solar system, stellar atmospheres, circumstellar shells, interstellar clouds, and possibly even in the early universe. Physical conditions are naturally different in the different situations, but there is unity in the underlying physics and chemistry in this diversity. Therefore, a need was felt to gather together astronomers, physicists and chemists in these and allied interdisciplinary fields to enrich each other with their experiences. This International Astronomical Union Symposium No.120 on Astrochemistry, the proceedings of which is this, has partially fulfilled this need. This symposium, held at the beautiful and scenic sea resort of Goa, India, between December 3-7, 1985, under the sponsorship of the IAU Commission No.34 and co-sponsorship of IAU Commissions 14, 15, 29 and 36, was attended by 116 registered participants with 19 accompanied guests from 19 countries. The scientific programme comprised of 34 review talks, 15 invited talks and 47 contributed poster papers, clima­ xed by a grand finale by Professor A. Dalgarno with an overview of th~ whole symposium. The Symposium covered almost all aspects of astro­ chemistry from the early universe to comets and meteorites, except iono­ spheres and planetary atmospheres. Basic atomic and molecular physics, experimental and observational results, and theoretical calculations and modelling, all were stressed.