Tumors of pheochrome tissue have been considered to be among the rarer tumors, but with increasing interest in all types of hypertension and with improvements in diagnostic methods, these tumors have been recognized more frequently than formerly. The syndrome of "paroxysmal hypertension" that has been considered typical of tumor of pheochrome cells is familiar to all, but with the finding of more of these tumors observers now realize that many of them produce symptoms of persistent unremitting hypertension resembling the so-called essential hypertension. It has also been shown that some tumors arising from pheochrome tissue, notably the carotid body, apparently do not cause the hypertensive symptoms. SYMPTOMS AND MANIFESTATIONS The usual symptom complex is either spontaneous or induced and consists of a pounding headache, a pronounced beating of the heart with epigastric distress and a constriction of the hands and feet, often associated with a sense of impending death, lasting