A case of tranylcypromine (Parnate) overdose is presented in which the main toxic effects were headache, obtundation, hypertension, and diffusely peaked T-waves on ECG. The latter effect, which occurred in the absence of hyperkalemia, has not been previously associated with monoamine oxidase inhibitors (MAOI). Recent case reports of tranylcypromine toxicity are briefly reviewed, confirming the potential for hypertension, hypotension, shock, hyperpyrexia, intracranial hemorrhage, agitation, hyperkinesis, coma and death in association with overdosage, or concommitant ingestion of sympathomimetic substances or other drugs. These ECG changes add to the worrisome list of potential toxicities in an era in which MAOI are finding increased clinical use.