Two preparations for studies of adrenergic transmitter release from arteries are described. Isolated segments of rabbit ear artery were incubated with (3H)-(-)-noradrenaline and the amounts of tritium released into the luminal perfusate and into the extraluminal superfusate were measured. Periarterial nerve stimulation at a frequency of 5 Hz increased the levels of radioactivity in the extraluminal superfusate. With higher frequencies of stimulation (20 and 50 Hz), there were increased levels of radioactivity in the perfusate and the superfusate, but over 90% of the total increase appeared in the extraluminal superfusate.