During a three-year period, drug-induced illness, excluding suicide attempts and drug abuse, accounted for 2.9% of admissions to a medical service. There were proportionately fewer admissions for patients under 61 years of age than for those over. A considerably greater number of white women than black women or men were affected. More than 6% of these patients died. Eight drugs (aspirin, digoxin, warfarin sodium, hydrochlorothiazide, prednisone, vincristine sulfate, norethindrone, and furosemide) produced a third of the illnesses. In 18% of the cases an over-the-counter drug was implicated. Hemorrhagic effects occurred frequently. The cardiovascular, gastrointestinal, and hemopoietic systems were most often involved. Drug allergy was the mechanism of the adverse drug effect in 17.6% of the illnesses. The remainder were due to pharmacological mechanisms. (JAMA 228:713-717, 1974)