The IAU symposium No. 150 "Astrochemistry of Cosmic Phenomena" was held at the beautiful and scenic town of Campos do Jordao, Sao Paulo, Brazil from August 5 to 9, 1991, and was attended by 111 registered participants with 17 accompanied guests from 19 countries. The symposium had a wide ranging discussion of the chemistry of astronomical environments with an emphasis on the description of molecular processes that critically influence the nature and evolution of astronomical objects and the identification of specific observations that directly address significant astronomical questions. The subject areas of the symposium included atomic and molecular processes at low and high temperatures and photon interactions, the chemical structure of molecular clouds in the Milky Way and in external galaxies, the chemistry of outflows and their interactions with the interstellar medium, the chemical connections between the interstellar medium and the solar system and pregalactic chemistry. The scientific programme comprised of review talks and con­ tributed papers, with a general introduction by Professor A. Dalgarno and a final overview of the whole symposium by Professor D. A. Williams. Financial supports from the Sao Paulo State Foundation Support (FAPESP), Brazilian National Research Council(CNPq), Finance Company of Studies and Projects (FINEP), Institute of Astronomy and Geophysics of University of Sao Paulo (IAG-USP) and Inter­ national Astronomical Union (IAU) are greatfully acknowledged. I am greatly indebted to Professor A.

Preface. Basic Studies. Early Universe. External Galaxies. Diffuse, Translucent and High-Latitude Clouds. Quiescent Clouds and Regions of Star Formation. Chemistry of Interface Regions. Near Stellar Environments. Solar System. Index.