Objective To investigate the predictive value of plasma gelsolin in the prognosis of patients with ST-sgement elevation myocardial infarction ( STEMI ) and undergone primary percutaneous coronary intervention ( PCI ) .Methods The study included 206 patients with STEMI and undergone primary PCI, 148 patients with stable angina pectoris and received elective PCI and 80 healthy volunteer as the health population (NP) control.Blood samples were taken at admission on day 1, 3, 5, 7 and 9 to determine the plasma gelsolin level .Patients′baseline clinical characteristics , blood biochemistry tests results , details of operation and their cardiovascular risk factors were recorded .Major adverse cardiovascular events (MACE) within one year were recorded.Results (1) Compared to the stable angina group and the NP group, the level of plasma gelsolin of STEMI patients were obviously decreased at various time points ( all P<0.05 ) .There were no statistical differences between the stable angina group and the NP group .( 2 ) Patients with STEMI were catagorized into MACE group (n=78) and non-MACE group (n=128) according their follow up record in 1 year.The level of plasma gelsolin in patients with MACE were lower than the non-MACE group ( P <0.05 ) with the minimum value detected on day 7.Among patients complicated with MACE (n=78), they were further devided into the deceased group (n=18) and the survival group (n=60).Plasma gelsolin levels were lower in the deceased group with satistical differences found on day 5, 7 and 9.(3) Single factor Logistic regression analysis showed that the level of plasma gelsolin on day 7 was independent risk factor of MACE within one year ( P =0.014 ) .( 4 ) Setting the cutoff value of plasma gelsolin on day 7 as 21.7 mg/L,the sensitivity and speciticity for the MACE in STEMI patients treated with primary PCI within one year were 82.1%and 81.4%respectively , with the area under the receiver operator characteristic curve ( ROC ) was 0.854 ( 95% confidence interval 0.732 -0.961 , P <0.01 ) . Conclusions Plasma gelsolin levels are correlated with the severity of STEMI lesions and plasma gelsolin can be used as predicting factor of prognosis .