Adrenocortical masses are among the most common tumors in humans. However, only a small proportion of these tumors cause endocrine diseases (such as primary hyperaldosteronism, hypercortisolism, hyperandrogenism, or hyperestrogenism), and less than 1% are malignant. In recent years, several of the molecular and cellular mechanisms involved in adrenal tumorigenesis have been unraveled. As a result, alterations in intercellular communication, local production of growth factors and cytokines, and aberrant expression of ectopic receptors on adrenal tumor cells have been implicated in adrenal cell growth, hyperplasia, tumor formation, and autonomous hormone production. Genetic and chromosomal abnormalities, including several chromosomal loci and the genes coding for p53, p57, and insulin-like growth factor II, have been reported in adrenal tumors. In addition, chromosomal markers have been identified in several familial syndromes associated with adrenal tumors; these include menin, which is responsible for multiple endocrine neoplasia type I, and the hybrid gene that causes glucocorticoid-remediable hyperaldosteronism. Algorithms for endocrine testing and imaging procedures are now available to codify screening for, confirmation of, and differentiation of causes of primary hyperaldosteronism and the Cushing syndrome. Improved radiologic, computerized radiologic, and magnetic resonance imaging techniques, as well as selective catheterization studies, are useful in localizing adrenal tumors and in distinguishing between benign and malignant lesions and between functional and nonfunctional nodules. Finally, recent refinements in the field of minimally invasive general surgery have made laparoscopic adrenalectomy the method of choice for removing adrenal tumors; this type of surgery allows shorter hospital stays, lower morbidity rates, and faster recovery.