This study aims to account for the microvariation in aspect choices in factual imperfective contexts in Polish. To this goal an online questionnaire was conducted in which the participants from western and eastern Poland were asked to fill in the missing verbs in presuppositional and existential factual contexts involving an Elaboration coherence relation. The study shows that perfective aspect is preferred in presuppositional factual contexts and imperfective is preferred in existential factual contexts in both regions. Additionally, imperfective is generally more often used in factual contexts in eastern Poland than in western Poland. The study accounts for the observed preferences by resorting to the interaction between the Elaboration relation and (in)definiteness of the temporal variable (introduced at the level of AspP) with respect to the temporal trace of a complex event decomposed in the first phase syntax.