This paper describes Spanish science teachers' thinking about issues concerning the nature of science (NOS) and the relationships connecting science, technology, and society (STS). The sample consisted of 774 in-service and pre-service teachers. The participants responded to a selection of items from the Questionnaire of Opinions on Science, Technology & Society in a multiple response model. These data were processed to generate the invariant indices that are used as the bases for subsequent quantitative and qualitative analyses. The overall results reflect moderately informed conceptions, and a detailed analysis by items, categories, and positions reveals a range of positive and negative conceptions about the topics of NOS dealt with in the questionnaire items. The implications of the findings for teaching and teacher training on the themes of NOS are discussed.