Easily performed prognostic rules are helpful for guiding the intensity of monitoring and treatment of patients. The aim of the present study was to compare the predictive value of the sepsis score and the Confusion, Respiratory rate (> or =30 breaths.min(-1)), Blood pressure (systolic value <90 mmHg or diastolic value < or =60 mmHg) and age > or =65 yrs (CRB-65) score in 105 patients with community-acquired pneumococcal pneumonia. In addition, the influence of timing of the antimicrobial treatment on outcome was investigated. The sepsis and the CRB-65 scores were used to allocate patients to subgroups with low, intermediate and high risk. Comparable, highly predictive values for mortality were found for both scores (sepsis score versus CRB-65): 1) low-risk group, 0 versus 0%; 2) intermediate-risk group, 0 versus 8.6%; 3) high-risk group, 30.6 versus 40%, with an area under the curve of 0.867 versus 0.845. Patients with ambulatory antibiotic pre-treatment had less severe disease with a lower acute physiology score, lower white blood cell count and a faster decline of C-reactive protein levels. No pre-treated patient died. In summary, both scores performed equally well in predicting mortality. The prediction of survival in the intermediate-risk group might be more accurate with the sepsis score. Pre-hospital antibiotic treatment was associated with less severe disease.