A 48-year-old man chronically treated with digitoxin and verapamil for prevention of atrial fibrillation voluntarily ingested 2.2 mg of digitoxin. Serum digitoxin concentrations and the urinary elimination of the drug were followed over a 12-day period. Urinary data indicate that a large percentage (50%) of the drug was eliminated renally despite administration of multiple doses of activated charcoal, cholestyramine and hyperosmotic laxatives. The possible interaction with two other drugs, heparin and verapamil, is also discussed.