Many new techniques are rapidly being developed and applied to the study of normal and neoplastic pituitary. DNA microarrays are a uniquely efficient method for simultaneously assessing the expression levels of thousands of genes, identifying disease subphenotypes, and predicting disease progression. This article reviews the utility of DNA microarray-based tumor profiling including recent developments and applications to pituitary biology in order to demonstrate how these new techniques are providing insights about basic aspects, clinical knowledge, and pharmacologic knowledge of the pituitary gland and about pituitary tumors.