26 deaths have been reported from various sources in 6824 angiocardiographic examinations (0.38%). 21 occurred in patients with congenital heart disease; 17 of these were cyanotic. 17 deaths occurred in children under 8 yrs. of age. 1 death occurred in a patient with renal arterial disease but with a normal heart. The commonest form of death was sudden respiratory arrest immediately or shortly after the injn. of contrast substance. Subdural hemorrhage occurred twice. It is concluded that the nature of the contrast substance injected, the number of injns., premedication and general anesthesia did not significantly influence the mortality. The incidence of death, however, was highest in patients with congenital heart disease, in patients receiving larger doses of the contrast substance, and in those examined in the horizontal posture.