Before the introduction of adrenergic blocking agents and pressor substances operative removal of a phaeochromocytoma was a hazardous procedure, with a mortality of up to 25% (Graham, 1951). A mortality of 50% has been reported in operations on patients with unsuspected turnours (Apgar and Papper, 1951 ;Riddell, Schull, Frist, and Baker, 1963