Mimetics in Japanese comprise both onomatopoeic expressions (phonomimes) and other ideophones (phenomimes; psychomimes), which do not imitate acoustic phenomena. They can appear in various syntactic positions and adopt the syntactic functions of nouns in a referential phrase, predicates, attributes in a noun phrase and adverbs, with the latter being the most common usage. Since the stem of mimetic expressions such as SUTON ("thump"), KIRARI ("flash"), KYAAA ("Aaaah!") or GAN-GAN ("pounding") cannot be altered and common suffixes such as /N/, /RI/ and /Q/ (glottal stop) cannot be inflected, the syntactic function of mimetics in Japanese is determined by their position in the sentence and the particles (postpositions) used to indicate their function within a larger constituent. In colloquial speech, these particles may also be omitted, which sometimes results in the syntactic position being the only indicator of the syntactic function. However, when contrasting the grammatical usage of mimetics in data sources from various speech registers, it becomes apparent that not all mimetics are used with all particles and in all syntactic positions. Moreover, some mimetics may be combined with certain particles in idiomatic contexts, but would be used differently in spontaneous speech. For this reason, it is not surprising that opinions vary greatly when it comes to determining the distribution of individual mimetics, and mimetics as a class. This often results in L2 learners of Japanese being confused by contradictory statements in dictionaries and textbooks, which may not necessarily reflect the actual usage of mimetics in spoken Japanese and thus constitute an obstacle to effective language learning. The focus of this thesis is a description of the variable use of selected mimetics in attributive contexts, to shed light on the factors underlying the variation, and to establish whether a language change has been taking place in recent years. Empirical data collected from dictionaries, corpora, surveys and interviews shows that sociolinguistic factors such as gender, age and media exposure may influence the grammatical preferences of native speakers and their perception of mimetics. For this reason, both linguistic and extra-linguistic factors have to be taken into account in order to establish a grammatical framework for mimetics in Japanese.