Overdose of tricyclic antidepressants (TCAs) leave no doubt that TCA drugs at high concentrations have serious cardiac effects. It has been assumed that, to a lesser extent, these effects would occur at usual therapeutic concentration. Recent prospective, plasma-level-controlled studies have improved our understanding of these drugs and proved these assumptions to be inaccurate. The most common serious cardiovascular complication of most tricyclic drugs is orthostatic hypotension. Tricyclic antidepressants are essentially free of any other serious adverse effects in depressed patients without cardiovascular disease. In patients with preexisting bundle-branch disease, there is a risk of heart block. On the other hand, patients with ventricular arrhythmias are likely to have their arrhythmias improve with TCA therapy. Finally, therapeutic doses of TCA have little adverse effect on left ventricular performance. As a result, TCA drugs can often be used to benefit depressed patients with overt heart disease.