The heterogeneous environment of information retrieval on the World Wide Web has brought the recognition for the need of interoperability among diverse systems to the fore. In subject retrieval, users encounter not only different vocabularies and schemes, but also different languages. As a result, there has been a flourish of projects in the last few years aimed at improving the interoperability among subject vocabularies and knowledge organization schemes, with some targeting different vocabularies and others focusing on different languages. This paper attempts to analyze the methods used in these projects. It begins with a brief overview and then examines in particular the approaches and methods used in recent efforts. (Contains 18 references.) (Author)