The aim of this bachelor's thesis is to examine how medical libraries use user studies and their results to develop their activities, as well as how they view their opportunities to clear the barriers users in user studies find that they have in their information seeking. The method used in the study is semi-structured interviews with five chief librarians at five different medical libraries in Sweden. The empirical data was analysed using qualitative content analysis. The theory used for analysing the results is Vedung's five models of use of evaluation: instrumental use, enlightenment use, legitimizing use, tactical use and ritual use. The result shows that medical libraries both take part in the results of user studies conducted at national level and own user studies. The respondents state that user studies are important and that they fill a function of finding out what users think about their activities. The results of user studies are mainly used as enlightenment, but also instrumental and legitimizing. The opportunities to clear barriers in the users' information seeking are many, but the most suggested is through marketing efforts. The conclusion is that user studies very well can be seen as a tool for developing the activities of medical libraries. If one uses the results of user studies in the instrumental, enlightening and legitimizing way that Vedung recommends and which the librarians in the study do in most cases, they can be very useful.