It is frequently described in international literature the possibility of toxicity by local anesthesics. The lidocaine is one of them. The problems with its local use are more frequent and known but topic toxicity is also possible. We want to describe a case of toxicity by topical administration of lidocaine (Xylocain) which caused neurological disease with convulsions, and cardiological disease with ventricular fibrillation, in a patient who came for a thyroplasty. Patient's evolution was satisfactory.