Abstract. The Estonian language makes a systematic distinction between total and partial objects on the basis of semantic and syntactic features: total objects occur in nominative or genitive, partial objects in partitive. However, in the case of the interrogative-relative pronoun mis ‘what’, the partitive mida in the expected partial object position can be replaced with the nominative mis. The aim of this paper is to determine which variables significantly affect this object case variation, how the variation differs between contemporary speech and archaic dialects and what might have possibly motivated the development of this variation. This study is based on the data in the Phonetic Corpus of Estonian Spontaneous Speech and the Corpus of ...