The influence of epinephrine on the cardiovascular effects of high (T5) peridural analgesia was studied in 19 human volunteers, each of whom received two injections. In 12, the effects of lidocaine alone were compared with those of lidocaine–epinephrine. Peridural analgesia with lidocaine alone produced small (5 to 10 per cent) changes in cardiac output (CO), total peripheral resistance (TPR) and mean arterial pressure (MAP). During peridural analgesia with Iidocaine–epinephrine a 49 per cent increase in CO and a 37 per cent decrease in TPR resulted in a 10 per cent decrease in MAP. All of these changes from control were statistically significant and were significantly greater than those produced by lidocaine alone. In another seven subjects, the effects of peridural injection of lidocaine–epinephrine were compared with those of injection of saline–epinephrine. The two solutions produced similar effects on the heart, but lidocaine–epinephrine solution caused a significantly greater decrease in TPR, and consequently in MAP, and a greater increase in leg blood flow than did saline–epinephrine solution.