A 32-year-old woman who complained of cough and hemoptysis was found to have a metastatic trophoblastic tumor in her lungs and in a supraclavicular lymph node. A regressed primary teratoma of the ovary was considered the most likely origin of the tumor. Sputum cytology showed malignant cells, many of which were in elongated fiberlike forms and some of which had orange-staining cytoplasm. These cytologic appearances of choriocarcinoma are described and compared with the brief descriptions available in the literature. The possibility of misdiagnosis as squamous carcinoma is emphasized. The correct diagnosis is of particular importance because choriocarcinoma of gestational origin, which is similar cytologically to that of teratomatous origin, responds well to chemotherapy.