The purpose of this article is to reveal whether traits can predict the core processes constituting borderline personality disorder (BPD). A large sample, including many with BPD, completed personality questionnaires and reported trigger and symptom experiences 5 times per day for 2 weeks. Multilevel modeling revealed first that symptoms were strongly contingent upon concurrent triggers and that BPD’s association to symptoms was largely due to this contingency. Second, personality traits predicted all components of this process: trigger experiences, symptom intensity, and the contingency of the symptoms on triggers. However, normal personality traits only partially accounted for the heightened experience of triggers, elevated symptoms, and magnified reactivity to triggers among those with BPD. Thus, normal personality traits are capable of explaining the dynamic processes characteristic of clinical disorders, meaning that normal traits can elucidate even complex dynamic clinical processes. However, traits appear to only partially contain the active ingredients responsible for the core process in BPD. Aspects of the disorder other than traits may account for the heightened trigger experience, elevated symptom intensity, and magnified reactivity to triggers in those with BPD. (PsycInfo Database Record (c) 2022 APA, all rights reserved)