MicroRNAs (miR) are small non-coding RNAs that regulate gene expression at the posttranscriptional level. MiR cluster 23/27/24 regulates angiogenesis, which is the process of forming new blood vessels by deposition of endothelial cells. There are 2 types of miR-27s found on endothelial cells: miR-27a and miR-27b. The actual mechanisms of miR-27s are not well known, but studies showed that overexpression of miR-27b increases angiogenesis. These results suggest that miR27b might be useful for treating patients with ischemic heart disease.