The majority of lung cancers associated with hyperamylasemia are adenocarcinomas. Here we report an unusual case of a 54-year-old male patient who complained of dyspnea, anterior chest wall discomfort and facial edema for one month, presenting with a huge mediastinal mass and hyperamylasemia complicated by pericardial effusion Histological evaluation of mediastinal mass revealed small cell carcinoma and pericardium showed nonspecific inflammation with fibrosis. The serum amylase had an electrophoretic mobility similar to that of salivary gland enzyme. There were no evidence of a salivary or pancreatic causes of hyperamylasemia. After chemotherapy, parenchymal lung lesions improved and hyperamylasemia disappeared. For the mannagement of peracardial effusion a pericardial window was forms(i. We concluded that the striking increase in serum amylase was due to the ectopic production of this enzyme by the tumor.