The relevance of a phobia-based conceptualization of fear for individuals with chronic pain has been much debated in the literature. This study investigated whether patients with highly fearful chronic low back pain show distinct physiological reaction patterns compared with less fearful patients when anticipating aversive back pain-related movements. We used an idiosyncratic fear induction paradigm and collected 2 different measures of autonomic nervous system activation and muscle tension in the lower back. We identified 2 distinct psychophysiological response patterns. One pattern was characterized by a moderate increase in skin conductance, interbeat interval (IBI) increase, and muscle tension increase in the lower back. This response was interpreted as an attention reaction to a moderately stressful event. The other pattern, found in 58% of the participants, was characterized by a higher skin conductance response, IBI decrease, and muscle tension increase in the lower back. According to Bradley and Lang defense cascade model, this response is typical of a fear reaction. Participants showing the psychophysiological pattern typical of fear also had elevated scores on some self-report measures of components of the fear-avoidance model, relative to participants showing the reaction pattern characteristic of attention. This study is the first to provide psychophysiological evidence for the fear-avoidance model of chronic pain.