The aim of this study was to assess whether measurements of serum amyloid A protein (SAA) could provide additional information on the severity of acute infection beyond that obtained from C-reactive protein (CRP) assays. The SAA and CRP concentrations were analysed from the sera of 334 children hospitalized for suspected pneumonia, meningitis or sepsis. SAA significantly correlated with CRP (r = 0.682, p < 0.001) and did not alone provide any further clinically useful information. By contrast, the median ratio (and interquartile range) of SAA to CRP varied significantly between clinical conditions of different severity and was significantly lower in the patients who died [1.9 (0.0-8.9)] than in those who survived [6.8 (3.2-13.6)] (p = 0.001).