Infections usually cause a change of metabolic pattern in biological fluids.The change of carboxylic acid (CA) levels in biological fluids was related with viral infectivity.Therefore, in this study altered levels of CA including keto acids were monitored in rat plasma after the injection with adenovirus, β-galactosidase expressing recombinant adenovirus (designated rAdLacZ) and RCA.Metabolic profiling analysis of CAs in plasma from control, rAdLacZ and RCA groups were performed by gas chromatography-mass spectrometry as their methoximation combined with tert-butyldimethylsilyl derivatives.When star symbol plotting was applied to the group mean values of CAs after normalization to the corresponding normal mean values, the resulting star patterns of the two infection groups were deformed and characteristic of each group.The present method allowed rapid discrimination of viral infection groups from normal group.