Beginning with the provocative report by Vakil1in 1949, and especially since Wilkins and his associates2introduced the drugs into the United States, preparations of Rauwolfia serpentina have been used with increasing frequency in the treatment of essential hypertension. In 1952 the highly purified alkaloid, reserpine, was isolated from Rauwolfia serpentina,3and this has been thought to be its chief active principle.4If this is true and if both preparations are equally effective, then it would seem preferable to use a single highly potent alkaloid rather than the mixture of various substances contained in the crude root. However, there has been some doubt as to whether reserpine is as efficacious as the whole root in the treatment of hypertension. We are here reporting the observations made in a controlled comparative study in which both the crude drug and reserpine were used in the treatment of essential