Periphrastic perfect is a notoriously difficult form of Old Church Slavonic (OCS) verbs, because it remains consistently resistant to any coherent semantic description. While the majority of OCS texts are (very literal) translations, readily calquing both lexical and grammatical features of Hellenistic Greek, the OCS perfect is almost unique in deviating drastically from this common trend. The present paper attempts to tackle the semantic puzzle of OCS perfect by analyzing examples from the Psalterium Sinaiticum, Euchologium Sinaiticum, Codex Suprasliensis, and Codex Marianus. A preliminary look at the examples indicates that one can hardly speak of OCS perfect as a unified grammatical value with one and the same range of uses in all available texts. Іt would be more profitable to establish the patterns of perfect use for individual documents. Different factors predetermining the choice between competing perfect and aorist forms in different OCS texts are discussed in the paper and illustrated by various examples. Іt is argued that there is a strong tendency to use Aorist in resultative contexts to refer to individual situations with an exact temporal location, whereas Perfect is predominantly used (i) to convey the interpretation of a previously introduced situation (as in Mk 14:8 ‘She hath done what she could: she is come aforehand to anoint my body to the burying’); (ii) to characterize the subject of the predication; and (iii) in existential contexts (‘the situation took place at least once in the past’).