Purpose: This study examines 3 hypotheses about the processing of "wh"-questions in both neurologically healthy adults and adults with Broca's aphasia. Method: We used an eye tracking while listening method with 32 unimpaired participants (Experiment 1) and 8 participants with Broca's aphasia (Experiment 2). Accuracy, response time, and online gaze data were collected. Results: In Experiment 1, we established a baseline for how unimpaired processing and comprehension of 4 types of "wh"-question (subject- and object-extracted "who"- and "which"-questions) manifest. There was no unambiguous support found for any of the 3 hypotheses in Experiment 1. In Experiment 2 with the Broca's participants, however, we found significantly lower accuracy, slower response times, and increased interference in our gaze data in the object-extracted "which"-questions relative to the other conditions. Conclusions: Our results provide support for the intervener hypothesis, which states that sentence constructions that contain an intervener (a lexical noun phrase) between a displaced noun phrase and its gap site result in a significant processing disadvantage relative to other constructions. We argue that this hypothesis offers a compelling explanation for the comprehension deficits seen in some participants with Broca's aphasia.