Pheochromocytomas and/or paragangliomas are rare, heterogeneous tumors of the chromaffin cells. Thirty percent of the patients presented with these diseases in a hereditary context. The biological diagnosis relies on the identification of excessive secretion of the metanephrines which are more sensitive and specific than those of catecholamines The published recommendations give the opportunity to choose between the free metanephrines and the fractionated metanephrines in sera or urines. The concentrations of the free plasmatic metanephrines reflect the ongoing production of tumor. They are little sensitive to the renal failure. The assay of the vanillylmandelic acid should be dropped because of its inefficiency. The assay of the chromogranin A in serum should be used in association with those of metanephrines in the diagnosis but also in the follow-up. Its role still has to be precised.