Lambert-Eaton myasthenic syndrome (LEMS) is an autoinmune idiopathic or paraneoplastic syndrome producing antibodies agaisnt presynaptic voltage calcium channels. The clinical features of patients with LEMS are muscle weakness and autonomic dysfunction. We report a 40 years old man with a four years history of proximal weakness, absent tendon reflexes and dry mouth. The diagnosis was confirmed by characteristic electromyographic findings, showing a low-amplitude muscle response that increased dramatically after activation. Circulating antibodies to voltage-gated calcium channel were present. The search for malignant tumors was negative. The patient was treated with prednisone and azathioprine and after four months, he was able to walk and signs of autonomic dysfunction started to subside