Truly adverse reactions to drugs, as distinguished from troublesome but acceptable side effects, often affect the gastrointestinal tract, in Cluff's series (1) of 714 patients on the Johns Hopkins medical wards during 3 months of 1964, one-third of the total reactions were gastrointestinal. He confirmed earlier studies by Barr (2), indicating that of patients admitted to his university service, 5% suffered from drug reactions, and of those, 30 R developed another drug reaction during hospitalization. About 14% of all patients developed an adverse reaction during hospitalization. Since the average patient receives 10-14 drugs during a hospitalization, and since only about 10% of significant, adverse reactions are vohmtarily reported, the potential scope of this hazard is enormous. Several factors predispose a patient to an adverse reaction to drugs. Three-quarters of the patients with allergic reactions to drugs had ulcer, ulcerative colitis or gastrointestinal neoplasms (3). These reactions occur more often in females, in patients who are given the drugs orally, in patients who receive a greater number of drugs (eleven as opposed to six drugs in those without drug reactions), and in patients with a history of drug allergy or systemic lupus erythematosus. There is a lack of epidemiologic data on other populations which are specifically at risk. When more than six