Hoarding, the accumulation of a large number of possessions and substantial clutter, is increasingly being recognized as an important public health concern. Emerging consensus suggests that hoarding is an independent phenomenon and it will likely be included as a new diagnosis (Hoarding Disorder) in the forthcoming revision to the DSM. An initial conceptual model of this condition has implicated information processing deficits and emotional distress as key components of hoarding disorder. Although it has shown promise, this model is in need of greater empirical support and verification. The present study reports on an investigation into information processing and affective responses in relation to hoarding. We compared adults meeting criteria for hoarding disorder (N=33) and community controls (N=30) using psychophysiological methodologies based on startle eyeblink responses. Prepulse inhibition of startle (PPI), a measure of sensorimotor gating used in previous studies of schizophrenia and OCD, was used to test for information processing deficits proposed to be involved in hoarding symptoms by the cognitive-behavioral model. Affective valence startle modulation (AVSM) was used to elucidate emotional processing in association with hoarding. We also compared hoarding and control group participants on startle reactivity at baseline and while undergoing a symptom-provocation stressor (discarding task). Contrary to our hypothesis, the hoarding and control group participants demonstrated comparable levels of PPI. There were also no group differences when considering comorbid diagnoses. PPI scores were not related to medication status. AVSM results revealed that both the hoarding and control groups demonstrated a linear pattern of startle modulation to pleasant, neutral and unpleasant stimuli respectively. The hoarding group demonstrated larger general startle reactivity compared to the control group, both at baseline and following the discarding task. We did not find group differences in PPI, indicating that hoarding disorder is not related to sensorimotor gating deficits. The hoarding and control groups had similar affective modulation of startle, but the hoarding group demonstrated higher general startle reactivity. Enhanced general startle suggests that hoarding disorder is characterized by enhanced defensive responding, as is noted in other anxiety disorders such as PTSD and GAD.