MicroRNAs (miRNAs) are endogenous small RNAs that play an important role in various physiological processes by downregulating target genes. Recently, plasma miRNAs have been investigated as biomarkers for various diseases. In this study, miRNA array analysis in various tissues showed that miR-124 is almost exclusively expressed in the central nervous system and neuronal cells, suggesting that it might be useful as a potential biomarker for neurological diseases. We examined whether plasma concentrations of brain-specific miRNA can serve as a biomarker for cerebral infarction, where the cerebral infarction was modeled by middle cerebral artery occlusion (MCAO) in the rat. Plasma concentrations of miR-124 were significantly elevated at 6 h, and remained elevated at 48 h after MCAO introduction. Thus, plasma concentration of miR-124 provides a promising candidate biomarker for early detection of cerebral infarction.