MicroRNAs are small RNAs that attenuate protein expression by comple-mentary binding to the 3¢-UTR of a target mRNA. Currently, very little is known about microRNAs after cerebral ischemia. In particular, micro-RNA-21 (miR-21) is a strong antiapoptotic factor in some biological systems. We investigated the role of miR-21 after stroke in the rat.