The present article describes basic facts about the interuniversity cooperative library service that has been in practice in Japan since mid-1990s by way of an ILL request message sending system called NACSIS-ILL. The study underlying the article is based on the data recorded by the system from 1994 to 2005. Among major findings are that the “Interlibrary Loan (ILL)” in the Japanese university context is very peculiar in that requests for photocopies of “foreign journal” articles are significantly predominant in 1990s; that, ironically, increase of requests for “domestic journal” articles, including those in nursing science in particular, is becoming conspicuous as if to match the decrease of requests for “foreign journal” articles, most of which have become available online through site licensing under consortial arrangements that began in 2002; that requests for book loan, which have only accounted for a small portion of requests, apparently increased as the union catalog database called NACSIS-CAT grew; that the system is remarkably efficient with the fill rates in lending/supplying constantly high and the average turnaround time generally less than a week; that while the original intention was construction of a mutually beneficiary collaborative system, there have been some libraries that mainly only request and others that mainly only supply, due partly to the existence of “subject foreign journal center” libraries which started in 1970s; and that some small or middle-sized libraries noticeably began to supply in recent years.