Episodic palpitations with throbbing headaches and profuse sweating with hypeension and tachycardia is pointing towards the clinical diagnosis of pheochromocytoma. MRI/ 18-F-DOPA findings are suggestive of pheochromocytoma. Rule of 10s for pheochromocytoma: - Ten percent of pheochromocytomas are extra-adrenal (occurring in sites such as the organs of Zuckerkandl and the carotid body) Ten percent of sporadic adrenal pheochromocytomas are bilateral. Ten percent of adrenal pheochromocytomas are biologically malignant, Ten percent of adrenal pheochromocytomas are not associated with hypeension. The most sensitive test to diagnose pheochromocytoma is estimation of plasma levels of metanephrines. Histopathologically, the tumor consists of clusters of polygonal or spindle shaped chromaffin cells suppoed by sustentacular cells in a nest like pattern which is also known as Zellballen pattern. Phenoxybenzamine is an irreversible alpha-adrenergic blocker is used in the treatment of pheochromocytoma. Phentolamine is a reversible alpha-adrenergic blocker is used as a challenge test in diagnosis of pheochromocytoma.