Background: Pain catastrophizing is a particularly harmful cognitive factor among patients with chronic pain, but little is known of mechanisms linking this factor to pain and disability.Purpose: The study examined whether attentional focus on sensory versus affective information about pain constitutes a path-way by which catastrophizing affects responses to painful stimuli.Methods: Participants were 82 chronic pain patients assigned randomly to sensory focus, affect focus, or control conditions. They underwent cold pressors first prior to and then following an information focus manipulation, and they completed the Pain Catastrophizing Scale (PCS).Results: Regressions produced significant Condition × PCS interaction effects on threshold and tolerance change from first to second cold pressor, such that PCS scores were significantly and negatively related to these changes in both sensory and affect focus conditions, but not in the control condition. Only a main effect for PCS scores emerged for self-reported pain changes. Solving regression equations for hypothetical PCS values (± 1 SD from the mean) revealed that (a) high catastrophizers decreased threshold and tolerance in the affect focus condition and showed no appreciable changes in sensory focus and (b) low catastrophziers showed increases in threshold and tolerance in sensory focus, but no appreciable changes in affect focus. Further, the degree to which patients focused on emotions during pain partly mediated effects of PCS scores on threshold and tolerance changes.Conclusion: Catastrophizing about pain may affect pain severity and distress of chronic pain patients through a bias toward processing the most disturbing elements of a painful stimulus.