The concept of internationalization has been seen as a buzz word and container concept. The meaning of internationalization includes everything that relates to international, meanwhile internationalization is losing its meaning. This study takes a practical approach to searching for some clarification of this concept. During the period 2009-2011, 73 key actors in the field of internationalization at 16 Dutch higher education institutions (HEIs) were interviewed. Among the 14 elements identified by this study as constituting the concept of internationalization, many may be commonly known. However, the value of this study is that it ranks their significance and provides a sound base for further comparative studies in other countries. Moreover, this study compares and contrasts the differing interpretations of what the pursuit of internationalization means in research universities and universities of applied sciences and concludes that internationalization is pursued differently in the two sectors and clarifies the cause of these differences. These sectoral differences are important but have so far been rarely acknowledged in the internationalization literature. Finally, knowledge about practitioners' perceptions of internationalization is not widely available in the education literature on internationalization. This study provides this knowledge based on the Dutch situation and argues that the current trend of theoretical development and general conceptualization in this field needs to recognize the actual practices, if our aim is to produce meaningful and feasible models/guidelines/frameworks that are recognizable by the practitioners.