Science, Technology, and Society' - STS - has become a major educational theme. There are many courses in schools, universities and other institutions, dealing with all sorts of topics such as the history of science, energy policy, industrial innovation, technology assessment, Third World development, scientific method, and so on. But what is this subject really about? Why shoud it be taught? Who should study it? What should they learn? How should the subject be approached? Who should teach it? These questions are being asked by both teachers and students in many fields of science, engineering, medicine, social studies, and the humanities. This informal account of the rationale of STS education shows how many diverse factors are involved - the philosophy and sociology of science and education, social and cultural objectives, political ideologies, vocational needs, scholarly standards, institutional capabilities etc., not to mention the practical realities of teaching and learning at all levels.