• The antiemetic possibilities of three drugs were studied in 554 surgical patients who were divided into five groups by using a table of random numbers. The contratest group (a) received a placebo in ampuls identified only by code letters; the test groups received (b) chlorpromazine, (c) 100 mg. of pentobarbital, (d) 150 mg. of pentobarbital, and (e) dimenhydrinate. The anesthesia was nitrous oxide—ether. Dimenhydrinate and pentobarbital in the 100 mg. dosage were ineffective. Pentobarbital in the 150 mg. dosage and chlorpromazine effectively reduced postoperative nausea, vomiting, and retching, but they seriously lowered blood pressure and delayed awakening; in addition, the pentobarbital caused confusion and excitement. None of the four antiemetic procedures tried can be recommended for routine postoperative use. Considerable protection against emetic symptoms was afforded by 150 mg. of pentobarbital given with a gastric tube in place. Females had more postoperative emetic symptoms than did males, but no difference was found in a comparison of intraperitoneal with extraperitoneal operations.