MicroRNAs are a class of small RNAs that are essential regulators of gene expression and act within the RNA-induced silencing complex to bind mRNAs and suppress translation. Alterations in microRNA expression have been shown to disrupt entire cellular pathways, contributing to a variety of human diseases. MicroRNAs remain difficult to measure due to their short length, relatively small number, sequence similarity, and difficulty to isolate from other small RNA fragments. Our research in this area has focused on: (1) assessing and improving methods to measure microRNA expression, (2) the potential of microRNAs as biomarkers of disease, and (3) quantifying microRNA expression profiles across cell types. Our long-term goal is to advance microRNA research by developing statistical methods that are tailored to the specific complexities of microRNA expression data.