This study examines predictions derived from Foa and Kozak's theory of emotional processing. We hypothesized that the provision of heart-rate feedback would facilitate emotional processing through a fuller activation of the participant's fear structure, and by focusing participants' attention on information that is incompatible with the fear structure, i.e., the interoceptive pattern of habituation. Nonclinical students (N = 54) showing marked claustrophobic fear received 30 min of self-directed exposure to a claustrophobic chamber. Three exposure conditions (heart-rate feedback, paced-tone control, and exposure only control) were examined across six 5-min exposure trials. Participants receiving heart-rate feedback displayed greater between-trial habituation across treatment trials and lower levels of fear at post-treatment. Treatment process findings failed to support the fear activation hypothesis. Implications of the findings for theories of fear reduction are discussed.