This conference is the second on the Science and Technology of Thin Film Superconductors. It proved to be an excellent forum for these specialists in thin film superconductivity. The conference, held April 30-May 4, 1990, in Denver, Colorado, hosted 170 researchers from 17 countries. The response to the conference again emphasized the need for a meeting devoted to the science and technology of thin film superconductors. The breadth of artic1es and advances made in this technology since the first conference in November 1988, reflect on the maturity of the topic. These proceedings contain artic1es on deposition methods by sputtering, e1ectron beam evaporation, resistive evaporation, laser ablation, chemical vapor deposition and electrodeposition, and on other studies related to substrates, thermodynamics of formation, grain boundaries and weak links, characterization, and some practical applications. The program committee was pleased with the quality of the publications and contributed articles. This conference was highlighted by a fuU day dedicated to presentations from the federallaboratories, discussing a wide range of topics on the fabrication, characterization, and theory of high-temperature superconductor thin films. Other highlights at the conference dealt with (1) critical parameters or problems in measuring critical current density and other important parameters, and (2) problems of scale-up, reproducibility, and amenability to device fabrication. It became evident from the presentations that three issues were developing into critical issues for the ultimate practical application of high temperature superconductor thin films."