A case of allergic reaction under treatment with a tricyclic drug, trimipramine, is described. The clinical manifestation was an acute, influenza-like syndrome with eosinophilic pleurisy and involvement of liver function. This case is compared with allergic reactions under antidepressant treatment described in the literature. The combination of pulmonary and hepatic involvement in an allergic reaction is not unusual, but has not thus far been described for tricyclic antidepressants. The importance of laboratory investigations during antidepressant therapy is emphasized.