Sampling from the inferior petrosal sinuses for ACTH levels differentiates Cushing disease from the ectopic ACTH syndrome in nearly all patients. Patients with corticotroph tumors have a petrosal-to-peripheral ACTH gradient of 2 or more, while patients with other causes of Cushing syndrome have lower gradients. Bilateral petrosal sinus sampling also often provides useful information on lateralization of the adenoma for the neurosurgeon. The widespread application of inferior petrosal sinus sampling has been limited by concerns about potential complications and by technical failures in the hands of less experienced radiologists. In this protocol, we compare ACTH levels in the internal jugular veins before and after CRH stimulation with those obtained by conventional inferior petrosal sinus sampling from patients with Cushing's syndrome. Obtaining blood from the jugular veins is a simple, practically risk-free procedure that could be accomplished easily in community hospitals on an outpatient basis. We hypothesize that corticotropin-releasing hormone (CRH) stimulation will increase ACTH production from corticotroph adenomas so that the diagnostic information from jugular venous sampling would be equivalent to that obtained by catheterization of the petrosal sinuses.