The radiographic appearance of the pulmonary metastases of choriocarcinoma and other malignancies of gestational trophoblastic origin is described. Quantitative, though not qualitative, differences from other large series in the literature are noted. These observations may more accurately reflect the experience with this disease in North America. Three basic types of metastases are described--typical, alveolar, and embolic with emphasis placed on the most common typical metastatic lesion. The possible relation of methotrexate therapy to alveolar metastases is queried. That residual pulmonary nodules in the appropriate clinical setting need not represent viable tumor is noted.