Efforts have been devoted to introduce in science curricula direct instruction for evaluating scientific reports on socioscientific issues. In this study, students' opinions on the SSI of mobile telephones effects have been investigated before and after a classroom activity designed to enable students to assess scientific data. Aspects of the nature of science raised by students interpreting available contradictory research evidence and making personal decision on this SSI have also been documented. Results indicated the central role of considerations of scientific evidence in students' decision making. Students tended to over-attribute significance to empirical processes in justifying viewpoints on the SSI of mobile phones and in suggesting how scientific disputes might be resolved.