Objective: In this study, it was aimed to investigate the effect of streptokinase therapy in ST elevation myocardial infarction (STEMI) and conventional therapy in non-ST elevation myocardial infarction (NSTEMI) patients on the thrombolysis in myocardial infarction (TIMI) risk index (TRI), B-type natriuretic peptide (BNP), and high-sensitive C-reactive protein (hs-CRP) levels. Methods: Eighty-six STEMI (male/female ratio: 65/21, mean age 57.52±9.87 years) and eighty NSTEMI patients (male/female ratio: 50/30, mean age 57.6±1.7 years) were included in this prospective observational study. Hs-CRP and BNP were measured and TIMI risk index was calculated in all patients. Coronary angiography was performed in all patients for principally determining TIMI flow rate. Chi-square test, paired t-test or Wilcoxon signed rank test, ANOVA and Spearman correlation analysis were used for statistical analysis where appropriate. Results: STEMI patients had higher systolic blood pressure, heart rate, BNP and hs-CRP values than NSTEMI patients at admission (p=0.04, p=0.01, p=0.001 and p=0.01, respectively). Thrombolytic therapy in STEMI patients resulted in statistically significant higher levels of BNP, hs-CRP and TRI values compared to baseline levels (p=0.001, p=0.001 and p=0.042, respectively). For NSTEMI patients conventional therapy yielded statistically significant decrease in systolic blood pressure levels and increase in TRI (p=0.001 and p=0.047, respectively). We found significantly lower BNP, hs-CRP in patients with higher TIMI flow rate (p=0.001 and p=0.001 respectively). Conclusion: Thrombolytic therapy with streptokinase failed to decrease BNP, hs-CRP and TRI values in STEMI patients. Conventional therapy in NSTEMI patients also resulted in higher TRI values than baseline values. We reached TIMI 3 flow in only 10.5% of the study patients, which may be responsible for our findings.