One hundred three (4.1%) of 2,499 patients hospitalized in a general medical ward were admitted because of an adverse drug reaction (ADR). Of 60 drugs involved, the most common were cardiac, antibiotic, and antineoplastic agents. The main reactions included skin rashes, bone marrow depression, arrhythmia, bleeding, and heart failure. Five (4.9%) of the patients died and 11 (10.7%) had life-threatening reactions. Risk factors predisposing to admissions due to ADR were: female sex, decreased renal function, polypragmasia, and the underlying disease. Twenty-seven percent of the admissions could have been avoided by a more careful choice and dosage of drug.