The American Association for the Advancement of Science (AAAS) has necessarily played a major role in the debates over choices and responsibilities arising from the advances of science and its applications in a rapidly changing world. The editor of this volume has selected articles, editorials, and letters from the AAAS journal "Science," from 1949-1988, that deal with: (1) scientific freedom and responsibility; (2) the difficult ethical questions that have arisen in the practice of science and its applications; (3) the risks and benefits of new technologies and the making of decisions concerning them; (4) the conflict between the traditional openness of science and the pressures for secrecy arising from concerns over national security by government officials; and (5) other related matters. (MVL)