This thesis examines how science is constructed in relation to the UFO-movement. More specifically, it examines how the Swedish UFO organisation UFO-Sverige (UFO-Sweden) has changed when it, during the years of 1970-1996, adopted scientific ambitions. At its origin UFO-Sverige was based on values associated with the New Age movement, eventually they started to embrace more scientific methods. It is the meeting between ufology and science within UFO-Sverige that is examined in this thesis. The theoretical basis is Thomas Gieryns concept of boundary-work. The concept of boundary-work is based on the notion that science is constructed in relation to non-science. It is when science is separated from non-science that the conditions for what is considered as science are determined. The conditions of science are therefore dependant on the context of the situation in which it is separated from non-science. The change in UFO-Sverige is in the thesis examined through its organisational statutes and articles from the organisations paper. Furthermore, a debate between UFO-Sverige and the sceptical organisation Vetenskap och Folkbildning (Science and the People’s Education), VoF, is analysed. The thesis concludes that in their transition UFO-Sverige is using the notion of unbiased, the possibility to document, and critical thinking as reference for their scientific validity. They have shifted their view on what is considered as rational to base their knowledge production on, from personal experience to observable evidence. Through the study of the debate between UFO-Sverige and VoF different views on how science should relate to unexplained phenomenon has emerged. VoF consider the probability of a new discovery prior an examination of an unexplained phenomenon. UFO-Sverige instead claims that you cannot determine the credibility of relevant findings before the phenomenon in questionis examined. The thesis also concludes that because UFO-Sverige is constructed as an Other to science, to which the identity of science is dependent upon, it won’t be accepted as valid science, even if they try to adapt to scientific terms. There is almost always a way to find something unscientific in their construction, and by doing so VoF can keep UFO-Sverige as their Other.