The extent of sensory and motor blockades was examined in 195 patients 5 and 20 min after four different techniques of brachial plexus block using 50 ml of 0.5% bupivacaine. The interscalene technique of Winnie (N = 50) resulted in a preferential blockade of the caudad portions of the cervical plexus and the cephalad portions of the brachial plexus. The supraclavicular approach of Kulenkampff (N = 55) and the subclavian perivascular approach of Winnie (N = 56) each resulted in a homogeneous blockade of the nerves of the brachial plexus. The Winnie modification of the axillary approach (N = 34) resulted in a preferential blockade of the caudad nerves of the brachial plexus. With all four techniques, motor blockade developed faster than sensory blockade. The difference in results suggests that the approach to be used should depend primarily upon the site of the operation. The perineural space enclosing the brachial plexus greatly facilitates the spread of a local anesthetic when injected; however, it is usually not filled completely or evenly.