Summary This paper investigates Korean scientific output, focusing on international collaboration patterns, through an analysis of journal publications. For the study, 44,534 publications, published by researchers affiliated with Korean institutions and indexed by SCI during the six years 1995-2000, were considered. The study period was divided into two periods to compare the international collaboration for three years 1995-1997 and 1998-2000. The results show a clear decrease in Korea's international collaboration level between the study periods even though the number of researchers as well as the total R&D expenditure decreased considerably after Korea's economic change. The decrease of international collaboration in Korean science was inversely associated with different determinants such as scientific size as well as national scientific infrastructure. This decreasing trend of international collaboration in Korean science was largely caused by discipline-to-discipline variations in coverage of the SCI database. Among the top-ten collaborating countries, only the Chinese and the Canadian share of collaborative publications with Korea increased between the two periods under consideration.