The occurrence of synchronous epithelial cancer of the lung and leiomyosarcoma of the small intestine is rare. We report here the case of a 62-year-old man with adenocarcinoma of the lung in clinical stage IIIB (T4N0M0). After two courses of chemotherapy (cisplatin, 80 mg/m2 and mitomycin C, 8 mg/m2) the patient developed symptoms of a small bowel obstruction. Palliative surgical resection was performed and a leiomyosarcoma of the small intestine was found and defined by an immunohistological study. The resection ameliorated the patient's symptoms. The patient died of disseminated adenocarcinoma 26 months following chemotherapy.