The appearance of an adrenocorticotropic hormone (ACTH)-producing tumor after bilateral adrenalectomy for Cushing disease was first described by Nelson in 1958. The syndrome that now bears his name was characterized by hyperpigmentation, a sellar mass, and increased plasma ACTH levels. The treatment of Cushing disease has changed drastically since the 1950s, when the choice was adrenalectomy. Thus, the occurrence, diagnosis, and treatment of Nelson syndrome have changed as well. In the modern era of high-resolution neuroimaging, transsphenoidal microneurosurgery, and stereotactic radiosurgery, Nelson syndrome has become a rare entity. The authors describe the history of the diagnosis and treatment of Nelson syndrome. In light of the changes described, the authors believe this disease must be reevaluated in the contemporary era and a modern paradigm adopted.