This article discusses the nature of Estonian aspect and case, proposing an analysis of Estonian verbal aspect, aspectual case, and clausal aspect. The focus is on the interaction of transitive telic verbs (write, win) and aspectual case at the level of the functional structure. The main discussion concerns the relationships between aspect and the object case alternation. The data set comprises Estonian transitive verbs with variable and invariant aspect and shows that clausal aspect ultimately depends on the object case. The objects of Estonian transitive verbs in active affirmative indicative clauses are marked with the partitive or the total case; the latter is also known as the accusative and the morphological genitive or nominative. The article presents a unification-based approach in LFG: the aspectual features of verbs and case are unified in the functional structure. The lexical entries for transitive verbs are provided with valued or unvalued aspectual features in the lexicon. If the verb fully determines sentential aspect, then the aspectual feature is valued in the functional specifications of the lexical entry of the verb; this is realized in the form of defining equations. If the aspect of the verb is variable, the entry's functional specifications have the form of existential constraints. As sentential aspect is fully determined by the total case, the functional specifications of the lexical entry of the total case are in the form of defining equations. The general well-formedness conditions on functional structures secure the sensitivity of aspectual case to verb classification.