An observation of a treatment with digitalis antibodies (Fab‐fragments) in a young child is presented. The elimination of this antidotum proved to be much slower than normally expected. In the patient's history, the disappearance of the Fab‐fragments out of the blood lasted 142 days with a half‐life of 15.6 days, whereas an elimination with a T½of 28 hours is accepted. Probably there has been intracellular penetration of the antibodies into the liver, caused by concomitant diseases (Hepatitis A and B infections). An “in vitro” experiment is reported. It demonstrates the equimolar binding of the Fab‐fragments for digoxin and shows that the elimination of the Fab‐fragments can be established by a routine radioimmunoassay of digoxin, in a