Pheochromocytomas are important but uncommon causes of hypertension. These tumors are harmful for the effects of the catecholamines (adrenalin, also known as epinephrine, and noradrenalin, also known as norepinephrine) which they secrete and by the physical presence of the tumors themselves and their potential to metastasize. We wish to study these tumors with positron emitting agents to characterize and contrast both the functional and metabolic activities. This will be accomplished using 11C-epinephrine (EPI) to examine the catecholamine uptake system and 2-[F-18]-fluoro-2-deoxy-D-glucose (FDG) to examine glucose metabolism. "