To assess the association of age and other potential risk factors with digoxin toxicity, adverse drug reactions to digoxin (ADRDIG) were studied in all patients (n = 1338) on digoxin therapy consecutively admitted to 41 clinical wards throughout Italy during 4 months in 1988. At the time of admission, 28 patients (2.1%) had evidence of ADRDIG. In multivariate logistic regression analysis, significant associations with ADRDIG were found for age > or = 80 years compared to age 65-79 years (OR = 2.75, 95% CI = 1.17-6.45), daily digoxin dosage of > or = 0.25 mg (OR = 2.51, 95% CI = 1.16-5.47), serum creatinine > or = 120 mumol/L (OR = 3.75, 95% CI = 1.69-8.32), and for treatment with amiodarone, propafenone, quinidine or verapamil (OR = 2.60, 95% CI = 1.07-6.30). Those aged < 65 years had a similar risk of digoxin toxicity as those aged 65-79 years (OR = 1.07, 95% CI = 0.28-4.12). Adverse drug reactions to digoxin were found in 1 in 50 patients hospitalized on digoxin therapy. Patients aged 65-79 years were not at increased risk for digoxin toxicity compared to younger patients, while advanced age (> or = 80 years) was an independent risk factor for this outcome.