Background:Patients with suspected pulmonary embolism (PE) should be evaluated for the clinical probability of PE using an applicable risk score. The Geneva prognostic score, the PE Severity Index (PESI), and its simplified version (sPESI) are well-known clinical prognostic scores for PE. The purpose of this study was to analyze these clinical scores as prognostic tools.Materials and Methods:A historical cohort study was conducted on patients with acute PE in Al-Zahra Teaching Hospital, Isfahan, Iran, from June 2013 to August 2014. To compare survival in the 1-month follow-up and factor-analyze mortality from the survival graph, Kaplan–Meier, and log-rank logistic regression were applied.Results:Two hundred and twenty four patients were assigned to two “low risk” and “high risk” groups using the three versions of “Simplified PESI, Original PESI, and Simplified Geneva.” They were followed for a period of 1 month after admission. The overall mortality rate within 1 month from diagnosis was about 24% (95% confidence interval, 21.4–27.2). The mortality rate of low risk PE patients was about 4% in the PESI, 17% in the Geneva, and <1% in the simplified PESI scales (P < 0.005). The mortality rate among high risk patients was 33%, 33.5%, and 27.5%, respectively.Conclusions:Among patients with acute PE, the simplified PESI model was able to accurately predict mortality rate for low risk patients. Among high risk patients, however, the difference between the three models in predicting prognosis was not significant.