Chronic lymphocytic leukemia (CLL) is the most common leukemia in the western world and is a very clinically heterogeneous disease for which better prognostic biomarkers are needed. Current prognostic markers exhibit both biological and technical limitations. MicroRNAs (miRNAs) are small endogenous, non-coding 22-nucleotide regulatory RNAs that have been shown to modulate hematopoietic lineage differentiation and play important gene-regulatory roles in disease processes. In this manuscript, we review miRNA biology and the association of specific miRNAs with CLL. Copyright © 2013. Published by Elsevier Inc.