Objective: Prolonged prehospital delay in persons experiencing acute coronary syndrome (ACS) remains a problem. Understanding which patients respond best to particular interventions designed to decrease delay time would provide mechanistic insights into the process by which interventions work. Methods: In the PROMOTION trial, 3522 at-risk patients were enrolled from 5 sites in the United States (56.4%), Australia and New Zealand; 490 (N= 272 intervention, N= 218 control) had an acute event within 2 years. Focusing on these 490, we (1) identified predictors of a rapid response to symptoms, (2) identified intervention group subjects with a change in these predictors over 3 months of follow-up, and (3) compared intervention group participants with and without the favorable response pattern. Hypothesized predictors of rapid response were increased perceived control and decreased anxiety. Knowledge, attitudes, and beliefs were hypothesized to differ between responders and non-responders. Results: Contrary to hypothesis, responders had low anxiety and low perceived control. Only 73 (26.8%) subjects showed this pattern 3 months following the intervention. No differences in ACS knowledge, attitudes, or beliefs were found. Conclusion: The results of this study challenge existing beliefs. Practice implications: New intervention approaches that focus on a realistic decrease in anxiety and perceived control are needed. © 2011 Elsevier Ireland Ltd.