Bupivacaine (Marcaine) hydrochloride, a long-acting local anesthetic drug, was used in concentrations of 0.25, 0.5, or 0.75 percent with and without a vasoconstrictor, in amounts ranging from 25 to over 600 mg, for caudal, epidural (peridural), or peripheral nerve block for 11,080 surgical, obstetrical, diagnostic, or therapeutic procedures. Onset of anesthesia occurred in 4 to 10 minutes and maximum anesthesia in 15 to 35 minutes. Concentrations of 0.25, 0.5, and 0.75 percent consistently produced complete sensory anesthesia of the integumentary and musculoskeletal systems. With 0.25 and 0.5 percent, motor blockade ranged from minimal to complete. In intra-abdominal surgery, only 0.75 percent consistently produced profound muscle relaxation. Fifteen systemic toxic reactions occurred, but no untoward sequelae resulted from them. One inadvertent subarachnoid injection of 110 mg resulted in a total spinal block with an uneventful recovery.