Three hundred and twenty-eight consecutive patients admitted to a department of medical gastroenterology were evaluated in a high-intensity study of drug-related hospitalizations (DRH). The drug events considered were adverse drug reaction and dose-related therapeutic failures (DTF). With regards to the 'definite' and 'probable' drug events, DRHs accounted for 26 admissions (7.9%; 95% confidence interval (CI), 5.2-11.4%), and with the additional inclusion of 'possible' drug events DRHs accounted for 39 admissions (11.9%; CI, 8.6-15.9%). Of these, five and seven admissions, respectively, were caused by DTF. Patients admitted because of drug events took significantly more drugs than others. An evaluation of the circumstances of the 26 'definite' or 'probable' DRH showed none to be 'definitely avoidable', 6 to be 'possibly avoidable', and 20 to be 'not avoidable' by efforts from the prescribing physicians. Gastroduodenal lesions causally related to non-steroidal anti-inflammatory drug (NSAID) or aspirin use accounted for 17 of the definite, probable, or possible DRHs (44%). Only 1 of the 11 cases related to NSAID use was rated as possibly avoidable by efforts from the health service personnel. In 13 cases self-medication with aspirin played a substantial role in the DRH. Self-medication was largely characterized by poor indication, uncontrolled use, polypharmacy, treatment of epigastric pain with aspirin, and the patient's unawareness of potential adverse reactions. This suggests the need for intensified information to the public concerning the adverse effects of aspirin and NSAID.