The results presented in the paper have arisen from an ongoing PhD project on Gender and Identity started in 2005 and will be finished in 2010. Taking gender theories (Connell, 2003, 2008; Thorne, 1993) as a point of departure the overall aim of the dissertation is to explore constructions of gender in preschool, preschool-classes and grade one. In the analysis constructions of gender as they appear in children’s interactions and in children’s and adults’ interactions will be explored. Of particular focus are crossing and borderwork (see Thorne, 1993). The empirical basis of the dissertation consists of two different kinds of empirical data presented in two studies. In the first study video recordings from the Preschool and School in Collaboration project [FISK – projektet] are re-analysed. The analysis takes its starting point from conversation analysis (CA) and for the first time the video recordings are analysed from a gender theoretical perspective. The second study follows the ethnographical tradition and consists of data collected from a separate fieldwork, mainly observations, carried out in a preschool-class. In Nordic (Swedish) research there are a relative lack of research concerning preschool classes, which is why a preschool-class where chosen for the second study. In the analysis of the data three overall themes of particular interest in terms of gender have been identified: order and discipline, gendered categorizations and body and intimacy. The results both show situations where gender is less distinct and situations where borderwork are expressed. Previous gender research shows that it is often harder for boys than girls to cross gender boundaries. My results, however, indicates that boys more frequently challenge stereotypical norms and act in ways that normally not are expected for boys. On the other hand other children quite often question this kind of behaviour and gender boundaries maintain.