SummarySix cases of phcochromocytoma observed between 1961 and 1969 are reported. The second part of the study is devoted to an analysis of the present methods of diagnosis : 1) accurate history; 2) determination of free catecholamines and of VMA in urine; 3) radiological techniques urography, presacral oxygen insufflation, aortography; 4) pharmacological tests of inhibition (Phentolamine) and of stimulation (Histamine). The third part describes the pharmacological effects of catecholamines in relation to the specific alpha and beta receptors, and emphasizes the peculiarities in the clinical picture brought about by the secretion of epinephrine. Finally, the pre-and post-operative cares an discussed, stressing the importance of correcting hypovolemia.