Tricyclic antidepressant overdose is a frequent diagnosis in the emergency room. It is responsible for a significant percentage of hospital admissions for observation and treatment. This is due to its cardiac (as well as neurologic) toxicity, and the difficulty in predicting its clinical gravity. The authors present this paper with two objectives in mind: 1) information about a common and significant cardiological emergency; 2) presentation of the methodology concerning systematic reviews of the literature. In this third (of four) articles, the prognosis of tryciclic antidepressant overdose is presented (in the two previous articles--published in previous issues of the Revista--we discussed the epidemiological aspects as well as the clinical presentation and the diagnosis). In the remaining paper we will present its management, and prevention. Note: this is the third of a series of four articles on the cardiac toxicity of tricyclic antidepressant overdose; the final article will be presented in the October issue of the Revista.