Entrepreneurial opportunities are found in literature to be discovered,recognized, and created by entrepreneurs. This thesis aims to explore andexplain the influences upon entrepreneurs in terms of knowledge, and knowledgesources, in the opportunity identification stage. However, even though it isfound in literature that knowledge is a main influencer in the first stage ofthe entrepreneurial process, the approaches to explain the influences onentrepreneurs for entrepreneurial opportunities are not consistent, whichcreates confusion about the sources of knowledge that influence entrepreneurs,in combination with the type of knowledge. In order to further explore andexplain the area, research is done, and cases are formed by interviewingentrepreneurs from eleven companies. The results from the interviews are thencompared, and related back to the literature findings. In the analysis it isfound that sources such as work-experience, education, hobbies, and role modelshelp entrepreneurs to gain knowledge in the industry where he or she havestarted a venture from an opportunity. These sources of knowledge havecontributed to market pull knowledge, and it is also found that there is arelationship between prior knowledge and alertness, which has to do with theability to find useful knowledge.