Analyzing compound nouns is one of the crucial issues for natural language processing systems, in particular for those systems that aim at a wide coverage of domaius. In this paper, we propose a mcthod to analyze structures of Japanese compound nouns by using both word collocations statistics and a thesaurus. An experiment is conducted with 160,000 word collocations to analyze comlmund nouns of with an average length of 4.9 characters. The accuracy of this method is about 80%.