A case of a 57-year-old man who presented with the clinical features of Eaton-Lambert syndrome preceding the diagnosis of lung adenocarcinoma at autopsy by 7 years, is reported. Although myasthenic syndrome is intimately associated with pulmonary small cell carcinoma, which connotes a grave prognosis, a small percentage of the tumor can be squamous cell carcinoma or adenocarcinoma, which may be resectable. Therefore, a continued search for evidence of intrathoracic neoplasm must be pursued following manifestations of myasthenic syndrome.