The ability of measurement of serum procalcitonin (PCT) levels to differentiate bacteremic from nonbacteremic infectious episodes in patients hospitalized for community-acquired infections was assessed. Serum samples were obtained from adult inpatients with fever to determine the serum PCT level, C-reactive protein (CRP) level, and erythrocyte sedimentation rate (ESR). Of 165 patients, 22 (13%) had bacteremic episodes and 143 (87%) had nonbacteremic episodes. PCT levels, CRP levels, and ESRs were significantly higher in bacteremic patients than in nonbacteremic patients (P<.001,.007, and.024, respectively). The best cutoff value for PCT was 0.4 ng/mL, which was associated with a negative predictive value of 98.8%. Area under the receiver operating characteristic curve was 0.83 for PCT, which was significantly higher than that for CRP (0.68; P<.0001) and ESR (0.65; P<.05). A serum PCT level of <0.4 ng/mL accurately rules out the diagnosis of bacteremia. The use of PCT assessment could help physicians limit the number of blood cultures to be processed and the number of antibiotic prescriptions.