We found previously that increased levels of polyamine oxidase (PAO) [acetylpolyamine oxidase (AcPAO) plus spermine oxidase (SMO)], and acrolein (CH(2)CHCHO) are good markers of stroke. We then investigated whether silent brain infarction (SBI) can be detected by measuring acrolein, PAO, or other biomarkers. Several biomarkers were measured in the plasma of 53 normal subjects and 44 subjects with SBI. It was found that the levels of protein-conjugated acrolein (PC-Acro), interleukin-6 (IL-6) and C-reactive protein (CRP) were significantly higher in SBI than in normal subjects. PAO was slightly higher in SBI than in normal subjects. Since the probability of SBI was increased with age, values were analyzed including age as a factor. When the combined measurements of PC-Acro, IL-6 and CRP were evaluated together with age using a receiver operating characteristic curve, SBI was indicated with 89% sensitivity and 91% specificity. The results indicate that measurement of PC-Acro together with IL-6 and CRP makes it possible to identify SBI with high sensitivity and specificity.