Experiments in dogs with ventricular fibrillation were carried out to determine the effects of epinephrine, plasma volume expansion and manual pressure over the abdomen upon carotid flow and arterial pressure during external cardiac compressions. Epinephrine given intravenously produced a significant increase in systolic arterial pressure but no significant change in caro-tid flow. Epinephrine given subcutaneously over the sternum in 2 mg increments had no effect on either systolic pressure or carotid flow. Both intravenously and intra-arterially administered dextran 75 improved carotid flow during external cardiac compressions, both routes being equally effective. Volume expansion, therefore, is indicated during external cardiac compressions even in normovolemic subjects, provided there is no pulmonary edema. Constant manual pressure exerted over the upper abdomen during external cardiac compressions produced a significant increase in carotid flow, but is not recommended because it promoted rupture of the liver.