Although gynecomastia is a well-defined paraneoplastic syndrome in patients with nonsmall cell lung cancer, the association with pleomorphic carcinoma has not been reported. A 50-yr-old man presented with bilateral gynecomastia and elevated serum beta-human chorionic gonadotropin (βhCG) level. Chest tomography showed a mass in the right middle lobe. Right middle lobectomy and mediastinal lymph node dissection were performed. βhCG levels decreased rapidly after surgery. Histological examination revealed pleomorphic carcinoma with positive immunostaining for βhCG. Serum βhCG levels began to increase gradually on postoperatively 4th month. Computed tomography detected recurrence and chemotherapy was started. After second cycle of chemotherapy, βhCG levels decreased dramatically again and tomography showed regression in mass. Patient died 6 months later due to brain metastasis. βhCG expression may be associated with aggressive clinical course and increased risk of recurrence, also βhCG levels may be used to evaluate therapy response in patients with pleomorphic carcinoma. © 2010 The Korean Academy of Medical Sciences.