Our aim was to develop a clinical prediction rule for detection of bacteremia in a cohort of patients observed prospectively at a reference center in Medellín, Colombia. The significant predictors of bacteremia were an age of >or=30 years (odds ratio [OR], 2.07; 95% confidence interval [CI], 1.19-3.60), a heart rate of >or=90 beats/min (OR, 1.90; 95% CI, 1.13-3.17), a temperature of >or=37.8 degrees C (OR, 2.42; 95% CI, 1.41-4.14), a leukocyte count of >or=12,000 cells/microL (OR, 2.40; 95% CI, 1.41-4.10), use of a central venous catheter (OR, 1.89; 95% CI, 1.02-3.50), and a length of hospitalization of >or=10 days (OR, 2.02; 95% CI, 1.25-3.24). The Hosmer-Lemeshow test revealed a goodness-of-fit of 2.99 (P=.981), and the area under the receiver operating characteristics curve was 0.7186. Simple variables obtained from the clinical history of patients are associated with bloodstream infection in a reproducible fashion and should be instrumental for prioritizing the requests for blood cultures by clinicians.