Pheochromocytoma is a rare neuroendocrine tumor with a highly variable presentation. There is lack of agreement about the most efficient and cost-effective methods for diagnosis and localization of the tumor, which can be lethal if not identified and treated promptly.Autopsy studies indicate that up to 50% of all cases remain undiagnosed until death. Between 30 and 35% of the tumors have a hereditary basis. Development of malignancy is highly variable -- from less than 5% to more than 50% depending on the mutation; there is currently no effective cure. This volume encompasses a number of themes in several sections: genetics and clinical decision-making; genetics, molecular pathways of tumorigenesis, and divergent phenotypes; kaleidoscopic presentations and a minefield for differential diagnosis of pheochromocytoma; biochemical diagnosis: can we reach consensus?; tumor localization and the evolving importance of functional imaging; and new molecular markers and targets for diagnosis and treatment of malignant pheochromocytoma.