This dataset makes available the sample of clauses used in the study "A corpus study of grammatical case forms in written and spoken Estonian: Frequency, distribution and grammatical role". It includes 751 clauses from the fiction subcorpus of the University of Tartu’s Balanced Corpus of Written Estonian (cl.ut.ee/korpused) and 758 clauses from the Corpus of Spoken Estonian, maintained by the University of Tartu’s research group of Spoken Estonian (not publicly available at the time of publication). The spoken language selection derives from a subset of everyday (face-to-face and telephone) conversations. The dataset includes both the randomly selected clauses and manual coding, described in the paper.