Behar et al reported that small doses of epidurql morphine are effective in the treatment of acute and chronic pain by direct action on the specific receptors in the substantia gelations of the posterior horn of the spinal cord. Brachial plexus blocks were performed in 217 cases in our hospital from Jun. 1979 to Aug. 1981. In an attempt to evaluate the postoperative pain relief, these cases were divided into two groups; the control and the experimental group. The two groups were subdivided into three according to the method of approach-supraclavicular, interscalene, and axillary. The cases complaining of pain within 8 hours after the block were 71/112(63.4%) in the control group, and 26/105(24.8%) in the experimental group: and the cases complaining of pain or noticing no pain after 8 hours following the block were 41/112(36.6%) in the control group and 79/105(75.2%) in the experimental group. The postoperative pain relief was remarkable especially in the interscalene and supraclavicular approach in the experimental group. We thought this was probably due to anatomical variance of the interscalene and supraclavicular approach nearer to the spinal cord and opiate receptors.