During the inhalation of cyclopropane in the cat, the intravenous injection of epinephrine produced cardiac arrhythmias. The intravenous injection of PLV-2 (2-phenyIalanine-8-lysine vasopressin) under similar circumstances did not produce cardiac arrhythmias. In man, the intravenous injection of epinephrine during cyclopropane, trichlorethylene, halothane and fluroxene inhalation produced cardiac arrhythmias. The intravenous and subcutaneous injection of PLV-2 during cyclopropane, trichlorethylene and halothane inhalation did not produce cardiac arrhythmias. In a preliminary clinical trial, PLV-2 was found to be a safe and effective local vasoconstrictor.