During the past few decades something interesting has occurred. The internationalization of firms has changed business between and in different countries. New technology and improved communication tools create opportunities for firms´ internationalization, which has led to increased internationalization today.The purpose of this dissertation is to explore different theoretical models applicability to firms’ internationalization today. The data collection consists both of primary –and secondary data. The primary data was collected through interviewing decision makers in leading positions in firms with insights of internationalization. Moreover, different perspectives of internationalization was elaborated in this research because interviews were established in firms from different industries. The secondary data collection consisted of information from the firms´ websites and the firms' annual reports to analyze the degree of internationalization. The combination of data collection provided better insights of the different firms´ internationalization. To be able to secure that this research is realistic, exploration of three different theoretical models that describe internationalization was implemented.The results show that some theoretical models are applicable to some firms and industries. Internationalization depends on two factors: What type of products the firm have, and what type of business the firm is in. Therefore, it internationalize accordingly. Thus, the theoretical models are created to focus on different internationalizations such as fast expansion and Step by Step expansion. Moreover, there are also different internationalization approaches in different industries. Firms have a unique business concept and, therefore, their internationalization processes are different from one another in some ways. This shows that one theoretical model cannot explain all the different types of internationalization. However, all three theoretical frameworks are applicable to today´s internationalization in different ways.