Aims: Negative emotions have an adverse effect on cardiac prognosis. We inves tigated whether social inhibition(inhibited self-expression in social interaction) modulates the effect of negative emotions on clinical outcome following percutaneous coronary intervention(PCI). Methods and results: Eight hundred and seventy-five consecutive patients from the RESEARCH registry(Erasmus Medical Centre, Rotterdam)completed depression, anxiety, negativity(negative emotions in general), and social inhibition scales 6 months following PCI. The endpoint was major adverse cardiac event(MACE- death, myocardial infarction, coronary artery bypass graft(CABG), or PCI) at 9 months following assessment. There were 100 MACE; patients who were high in both negativity and inhibition were at increased risk of MACE(38/254=15% ) when compared with high negativity/low inhibition patients(13/136=10% ; P=0.018). Depression(P=0.23) or anxiety(P= 0.63) did not explain away this moderating effect of inhibition. High negativity/high inhibition(HR=1.92, 95% CI 1.22- 3.01, P=0.005) and previous CABG(HR=1.90, 95% CI 1.04- 3.47,P=0.038) were independent predictors of MACE. Patients with high negativity but low inhibition were not at increased risk(P=0.76). High negativity/high inhibition also independently predicted death/MI(n=20) as a more specific endpoint(HR=5.85, P=0.001). Conclusion: The interaction effect of social inhibition and negative emotions, rather than negative emotions per se, predicted poor clinical outcome following PCI. Social inhibition should not be overlooked as a modulating factor. Aims: Negative emotions have an adverse effect on cardiac prognosis. We inves tigated whether social inhibition (inhibit self-expression in social interaction) modulates the effect of negative emotions on clinical outcome following percutaneous coronary intervention (PCI). Methods and results: Eight hundred and seventy-five consecutive patients from the RESEARCH registry (Erasmus Medical Center, Rotterdam) completed depression, anxiety, negativity (negative emotions in general), and social inhibition scales 6 months following PCI. The endpoint was major adverse cardiac event , there were 100 MACE; patients who were high in both negativity and inhibition were at increased risk of MACE (38/254 = 15%) when compared with high negativity / low inhibition patients (13/136 = 10%; P = 0.018). Depression (P = 0.23) or anxiety (P = 0.63) did not explain away this moderating effect of inhibition. High Negative / high inhibition (HR = 1.92, 95% CI 1.22-3.01, P = 0.005) previous versus CABG (HR = 1.90, 95% CI 1.04-3.47, P = 0.038) were independent predictors of MACE. Patients with high negativity but Low inhibition were not at increased risk (P = 0.76). High negativity / high inhibition also carried predicted death / MI (n = 20) as a more specific endpoint (HR = 5.85, social inhibition and negative emotions, rather than negative emotions per se, predicted poor clinical outcome the following PCI. Social inhibition should not be overlooked as a modulating factor.