The literature concerning possible cardiotoxic effects of lithium therapy in man is reviewed. Reports indicate a high frequency of electrocardiographic T wave morphology changes with lithium therapy. Therapeutic and toxic levels of lithium have infrequently been associated with serious cardiac dysfunction. Of particular concern are cases of sinus mode dysfunction or sinoatrial block and the appearance or aggravation of ventricular irritability. The incidence of cardiac complications may increase with age. The necessity or cardiac screening and monitoring of patients receiving lithium is discussed.