Rapid identification of infection has a major impact on the clinical course, management, and outcome of critically ill intensive care unit (ICU) patients. We compared the results of PCR and procalcitonin with blood culture for ICU patients suspected of having septicemia. Ninety patients (60 patients meeting the criteria for sepsis and 30 patients not meeting the criteria for sepsis) were evaluated. Compared with blood culture as the gold standard, the sensitivity, specificity, and positive and negative predictive values for PCR were 100%, 43.33%, 46.87%, and 100%, respectively, and for procalcitonin were 100%, 61.66%, 56.6%, and 100%, respectively. The average times required to produce a final result were as follows: PCR, 10 h; blood culture, 33 h; procalcitonin, 45 min. Both PCR and procalcitonin may be useful as rapid tests for detecting septicemia but compared with blood cultures lacked specificity.