Teachers' scientific knowledge about societal science issues must be one of the prerequisites for the process of science teaching. Innovation in science teaching and its implications for students' scientific literacy depends on the understanding that teachers bring with them into the classroom. The purpose of this study was to investigate how Portuguese teachers judge their own knowledge about 28 societal science issues. The exploratory survey involved 464 teachers from primary school to university level, teaching science and nonscience courses. The issues were selected on the basis of their social relevance and were concerned with such things radioactivity, consumer education, environmental problems, and food. Results indicate that in all of the groups, more than 50% of the teachers thought that they knew very little or just a little about the majority of the themes. It is argued that if this situation is maintained, the scientific literacy of their students will probably be at risk. (PVD)