It is generally assumed that there is a negative correlation between national scientific size and amount of international research collaboration: The larger the size is of the national scientific arena, the lesser the amount of international research collaboration. In this study, the collaboration pattern of 49 universities is analysed and a comparison is made between the Northern European and American universities in our sample. It was found that the American universities have more national and less international collaboration than the European ones. However, for the European universities there are no impact of national size although the countries differ much in scientific size. This deviation from the general trend indicates that the above-mentioned explanation is too simple and that national scientific size does not correlate negatively with the amount of international research collaboration without exceptions.