Introduction & Objective: Less than 2% of all pregnancies are ectopic. Ruptured ectopic pregnancy (EP) remains the leading cause of pregnancy related maternal death in the first trimester. The greatest danger is related to undiagnosed early stage of tubal rupture. The aim of study is the dertermination of ability of the shock index in identifying ruptured ectopic pregnancy Materials & Methods: This cross sectional survey was conducted on 99 patients with ectopic pregnancy in Rasht's Alzahra hospital. We calculated shock index for all patients and then we calculated sensitivity, spicifity, positive and negative predictive values for each index. We determined the cut-off point of shock index with Roc curve and evaluated the correlation between shock index and hemoperitoneum. Statistical significans for variables were determined with the x2, Student t test, Pearson coefficient and logistic regression. All statistical calculations were done with Stat.V8, SPSS.15. Results: 38 of the 99 patients had ruptured EP and 61 of 99 patients had unruptured EP. The mean of shock index in ruptured group was 0.99±0.3 and in the unruptured group was 0.82±0.2 .There was significant difference between these two groups (P=0.001). The cut off point of shock index was ≥ 0.89.There was a significant correlation between hemoperitoneum and shock index (P≤ 0.001; r =0.54). Conclusions: The shock index ≥ 0.89 is a valuable predictive factor for Ruptured EP and has correlation with Hemoperitoneum.