Objective: One must first experience a traumatic event (Criterion A in the Diagnostic and Statistical Manual of Mental Disorders; 5th ed.; DSM–5; American Psychiatric Association [APA], 2013) to be diagnosed with posttraumatic stress disorder (PTSD). Standard procedures for assessing Criterion A (i.e., the “worst-event” method) may result in misidentification of trauma exposure status. The purpose of this Internet-based study was to obtain an estimate of the percent of an adult sample that is misidentified as non-Criterion A through use of this method. Method: Two separate samples completed the extended version of the Life Events Checklist for DSM–5 (LEC-5; Weathers, Blake, et al., 2013b). Sample 1 participants (N = 579) completed the LEC-5 via the traditional worst-event method, while Sample 2 participants (N = 569) completed follow-up questions for every event endorsed on the LEC-5, as well as a measure of posttraumatic stress symptoms. Results: The majority of each sample identified a worst event that met Criterion A (Sample 1 = 58.5%; Sample 2 = 54.3%). Of the 202 participants in Sample 2 whose worst event did not meet Criterion A, 69.6% reported at least one other Criterion A event. Additionally, posttraumatic stress symptoms (i.e., severity and factor structure) in Sample 2 did not differ between those with a worst event that met Criterion A and those with a secondary event that met Criterion A, even though the identified worst event did not. Conclusions: When assessing trauma exposure via self-report, a written narrative and follow-up questions should be requested for all events that are endorsed.