Tricyclic antidepressant overdosage may be complicated by cardiac arrhythmias, which were sometimes difficult to treat prior to the use of sodium bicarbonate. Experiments have been done with several antiarrhythmics in an attempt to define the optimum treatment. Sodium bicarbonate proved the most effective experimentally and this supports our clinical experience. Physostigmine is a useful second drug, having beneficial effects against arrhythmias and central nervous system manifestations of toxicity. Practolol, although reversing the arrhythmias, tends to cause hypotension. Other drugs tried were less effective.