Japanese adjectives have received a fair amount of attention for their intriguing morphological and diachronic properties. Adjectives have also been discussed in the typological literature, largely in terms of their status as a lexical category vis-à-vis nouns and verbs. Rather little research has been done, however, on the everyday use of adjectives in Japanese conversation. This paper aims to show that (a) adjective usage in conversation is intricately bound up with fixedness and frequency; (b) a usage-based approach reveals that interactional and cognitive practices are deeply intertwined in this lexical category for Japanese speakers; (c) these facts reflect the nature of human language as an emergent phenomenon. Based on a substantial corpus of Japanese conversations, the paper finds that (a) attributive adjectives are very rare; (b) among predicative adjectives, as well as the rare attributive adjectives, the most frequently occurring forms strongly tend to be associated with various types of fixedness, demonstrating its central status in our attempt to represent the grammar for real speakers.