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 second (of four) articles, the clinical presentation and diagnosis of tricyclic antidepressant overdose are presented (in the first article--published in the previous issue of the Journal--we discussed the epidemiological aspects). In the remaining two papers we will present its management, prognosis and prevention. NOTE: This is the second of a series of four articles on the cardiac toxicity of tricyclic antidepressant overdose; the next two articles will be presented in the September and October issues of the Revista.