An adverse drug reaction monitoring program was developed in ten geriatric nursing care facilities with a population of 826 patients. Over a two year period, the incidence of moderate to severe adverse reactions was decreased from 27 to 20 percent. Digitalis glycosides, antipsychotics, sedatives and hypnotics, diuretics, and anti-inflammatory agents were responsible for more than three quarters of the reactions. Elderly females receiving large numbers of drugs and patients having a history of a previous reaction were found to be at high risk of experiencing an adverse effect. A substantial reduction in the number of drug-related acute care hospital admissions and a decrease in drug consumption demonstrated the cost effectiveness of the program. The response of other health care professionals to the program was excellent. A Patient Assessment Form was developed to assist in the quarterly review of patient medications. Guidelines for monitoring adverse drug reactions in nursing care facilities are suggested to aid other pharmacists in the implementation of similar clinical services.