THE PHYSICIAN is commonly faced with the problem of patients with nausea and vomiting of varying degrees of severity. Among the antiemetic drugs that are now available to fill this need, prochlorperazine and trimethobenzamide hydrochloride have both been widely used, and both of these agents have individually been subjected to studies comparing their effects with placebo.1-3 Most of the previous tests with these drugs have been performed in a hospital setting. Furthermore, there is very little information comparing the efficacy of trimethobenzamide and prochlorperazine after systemic administration. The present study will concern itself with a comparative evaluation of prochlorperazine, trimethobenzamide, and placebo given by the intramuscular route to a predominantly ambulatory group of patients. Method The subjects of this experiment were of both inpatient and outpatient status and were not restricted as to sex. The only limitations were the exclusion of gravidas and persons below the age of 13