OBJECTIVE To investigate the relationship between clinical conditions typically observed in the geriatric patients (geriatric conditions) and adverse drug reactions in older patients admitted to acute care hospitals. METHODS Prospective observational study conducted in 11 acute care medical wards throughout Italy. METHODS Five hundred six patients aged 65 years or older consecutively admitted to participating wards. METHODS The outcome of the study was the occurrence of any adverse drug reactions during the hospital stay. Geriatric conditions considered in the analysis were basic activities of daily living, history of falls, slow walking speed, malnutrition, dementia, depression, 1 or more unplanned admissions in the previous 3 months, history of stroke, unintentional weight loss, and exhaustion. The relationship between risk factors and outcomes was assessed using logistic regression. RESULTS Female gender (odds ratio [OR] 2.29; 95% confidence interval [CI] 1.18-4.45) and number of medications taken during hospitalization (OR 1.12; 95% CI 1.06-1.18), but not individual Geriatric conditions, were associated with the outcome after correction for potential confounders. However, the simultaneous presence of history of falls and dependency in at least 1 activities of daily living (OR 2.18; 95% CI 1.13-4.19) was associated with adverse drug reactions during stay. CONCLUSIONS The simultaneous presence of history of falls and dependency in at least one activity of daily living defines a condition of particular vulnerability of elderly hospitalized patients to adverse drug reactions. Physicians should be aware of this high-risk condition when prescribing new drugs to disabled older people.