Socioscientific issues, SSI, can briefly be described as societal issues in which science plays a role. Dealing with SSI in science education is a means to prepare and empower students for active and responsible participation in a complex, democratic society. The implementation of SSI-based teaching calls for classroom practices in which scientific evidence alongside for example social and ethical perspectives are considered. Discourse-based teaching activities are emphasized as a means to provide opportunities for students to practice negotiations of SSI and explore diverse viewpoints on the issues. Dealing with SSI in science teaching is recognized as a challenging task for science teachers. This thesis aims to provide knowledge to support the implementation of SSI-based science teaching. Three studies involving two upper secondary school science teachers are performed to achieve this aim. The first study makes use of video-stimulated discussions to investigate the two teachers’reflections on their classroom practices while they implement SSI throughout an academic year. The second study utilizes the concept positioning as a tool to identify and describe the ways in which one teacher’s interactions with students during group work make available different parts for the students to play as participants, when dealing with SSI in the classroom. The third study makes use of the concept communicative approach to investigate how the two teachers’ management of classroom discussions sets conditions for the consideration of multiple perspectives relevant to SSI, including the students’ viewpoints. The results provide knowledge useful when making considerations about the design and enactment of teaching activities in relation to specific educational goals. The results suggest that a specific challenge with designing and enacting SSI-based teaching activities is to balance between controlling and directing the teaching activities to promote specific learning goals and providing space for students’ participation and perspectives. The results of employing the analytical tools elucidate how this challenge can play out in classroom practice and contribute with knowledge of the ways in which teachers’ discursive practices play a role in addressing this challenge. Strategies to support teachers’ implementation of SSI-based teaching that take account of teachers’ existing practices are discussed.