Background Acute myocardial infarction (AMI) is a common cardiac emergency with high mortality.Serum soluble ST2 (sST2) is a new emerging biomarker of cardiac diseases.The present study is to investigate the predictive value of sST2 and interleukin-33 (IL-33) for risk stratification and prognosis in patients with AMI.Methods Fifty-nine patients with AMI,whose chief complaint was chest pain or dyspnea,were selected for our study.Physical examination,chest radiograph,electrocardiograph (ECG),biomarkers of myocardial infarction,NT-proBNP,echocardiography and other relevant examinations were performed to confirm the diagnosis of AMI.Thirty-six healthy people were chosen as the control group.Serum samples from these subjects (patients within 24 hours after acute attack) were collected and the levels of sST2 and IL-33 were assayed by enzyme-linked immuno-sorbent assay (ELISA) kit.The follow-up was performed on the 7th day,28th day,3rd month and 6th month after acute attack.According to the follow-up results we defined the end of observation as recurrence of AMI or any causes of death.Results Median sST2 level of the control group was 9.38ng/ml and that of AMI patients was 29.06ng/ml.Compared with the control group,sST2 expression in the AMI group was significantly different (P＜0.001).In contrast,the IL-33 level showed no significant difference between the two groups.Serum sST2 was a predictive factor independent of other variables and may provide complementary information to NT-proBNP or GRACE risk score.IL-33 had no relationship to recurrence of AMI.Both sST2 and the IL-33/sST2 ratio were correlated with the 6-month prognosis; areas under the ROC curve were 0.938 and 0.920 respectively.Conclusions Early in the course (＜24 hours) of AMI,sST2 usually increases markedly.The increase of sST2 has an independent predictive value for the prognosis in AMI patients and provides complementary information to NT-proBNP or GRACE risk score.The IL-33/sST2 ratio correlates with the 6-month prognosis of AMI patients.However,there is no significant relationship between IL-33 and the prognosis of AMI patients.