This article focuses on the molecular events associated with pituitary tumorigenesis. An accurate description of the molecular pathogenesis of pituitary adenomas will have an important impact on clinical practice: identification of specific molecular markers of tumor invasiveness and recurrence will allow earlier therapeutic intervention and selection of appropriate follow-up protocols; family screening may become practically feasible; and potent subcellular therapies may be developed for patients with nonfunctioning tumors, in whom nonsurgical therapies are ineffective, and for those with resistant hormone-secreting tumors.