The purpose of this study is to discuss notions of femininity and masculinity in situations of argumentation among Swedish upper-secondary students who are studying Natural Science. The empirical material is drawn from an ethnographic inspired study, where I followed a group of students in all of their science teaching throughout a semester. This study includes three classroom situations where the students are given a task to play roles where they either argue for or against nuclear power and where they are asked to argue for or against genetically engineered organisms. The students also asked to defend the position of one country in negotiations to limit greenhouse gas emissions in an international climate conference. This study will focus on relational situations at the micro level that are related to masculinities and femininities at the macro-level. The results show how the constructions of argumentation in the role playing tasks are based on an economic terminology and rationality, which can be said to represent a masculine approach. In contrast, the discussions that followed the role playing allowed for affective presentations, which are often regarded as feminine. This study discusses how a critical perspective can contribute to the awareness of the logic of these rendered performances.