To present a case that demonstrates the evolution of a pheochromocytoma over a several-year period and to emphasize the importance of a thorough work-up for pheochromocytoma in patients with neurofibromatosis type 1 (NF1) and hypertension.We review the long-term clinical, biochemical, and imaging findings in a man with a complex medical history of hypertension, NF1, and cardiomyopathy.A 44-year-old man, with a well-documented history of headaches, hypertension, and NF1, was referred for evaluation of a right adrenal enlargement. He had developed cardiomyopathy and undergone an evaluation for cardiac transplantation. Initial computed tomography revealed subtle asymmetry in the upper right adrenal gland. Biochemical studies for pheochromocytoma yielded equivocal findings, with a 1.5-fold elevation in the urinary norepinephrine and near-normal urinary metanephrine level. Because 131I-metaiodobenzylguanidine imaging showed no tracer uptake in the area of the right adrenal gland, the patient was thought not to have a pheochromocytoma. The patient eventually underwent cardiac transplantation and did well. On reassessment 3 1/2 years later, he was found to have a larger right adrenal mass. The second endocrine evaluation demonstrated substantial elevation in the urinary metanephrine level, and the patient underwent laparoscopic right adrenalectomy to remove the tumor (3.5 by 3.0 by 2.5 cm), which proved to be a pheochromocytoma.This case shows that a pheochromocytoma can be difficult to diagnose and can evolve to become a large, biochemically active tumor. It is imperative that patients with an adrenal tumor undergo periodic reevaluation to ensure that the tumor remains stable in size. If the tumor enlarges, further biochemical testing is warranted.