Objectives: Eosinophil-associated diseases are an emerging health problem that include a diverse set of diseases ranging from asthma and allergies to Loeffler's syndrome and eosinophilic esophagitis. The commonality in all of these diseases is the inappropriate proliferation and effector activity of eosinophils, a class of granulocytic leukocytes. Understanding the mechanisms by which this cell type proliferates, differentiates, and becomes active during normal and disease states is of the utmost importance. MicroRNAs (miRNAs) and other epigenetic factors play integral roles in the control of a variety of normal cellular events including differentiation. However, the role of these epigenetic factors in determining eosinophil fate and activity is not well understood. The goals of this study are to define the epigenetic elements critical for eosinophil development and activity. Methods: A combination of primary cells and inducible cell lines will be used to dissect the epigenetic elements involved in eosinophil differentiation and function. MicroRNA expression will be assessed by means of quantitative real-time PCR (qPCR). Results: MiR-125a, miR-126, and miR-194 were expressed at significantly higher rates in the eosinophil differentiated cells as compared to control cells. Conclusions: The expression of select miRNAs was significantly altered during eosinophil development.