Abstract. Waka is a form of traditional Japanese poetry with a 1300year history. In this paper, we attempt to discover characteristics common to a collection of waka poems. As a formalism for characteristics, we use regular patterns where the constant parts are limited to sequences of auxiliary verbs and postpositional particles. We call such patterns fushi. The problem is to find automatically significant fushi patterns that characterize the poems. Solving this problem requires a reliable significance measure for the patterns. Br