Diphenylhydantoin sodium, glucose, and β-diethylaminoethyl diphenylpropylacetate hydrochloride were tested for their effects upon the cyclopropane-epinephrine arrhythmias. Diphenylhydantoin in a small dose enhanced the arrhythmias and in a larger dose controlled them when given by vein, but its action following oral administration was uncertain. Glucose increased both the duration and the severity of ventricular ectopic rhythms while β-diethylaminoethyl diphenylpropylacetate increased the dose of epinephrine which initiated them.