Metastatic gestational trophoblastic disease poses problems in diagnosis and management and has a poorer prognosis than the non-metastatic variant. The lung is the most common site of metastases. This paper reviews 97 patients with pulmonary metastasis developing after gestational trophoblastic disease who were seen at one centre over 26 years. Most patients had an antecedent molar pregnancy but an associated choriocarcinomatous lesion in the uterus was absent in the majority. In many patients the pulmonary lesion was asymptomatic. Whilst chemotherapy was the treatment of choice, selective thoracotomy in cases with solitary lung nodules reduced the treatment time and need for aggressive multi-drug combination regimens. The overall survival rate at 2 years after diagnosis was 65%. A higher mortality was found when the antecedent pregnancy ended at term, when the time interval between the preceding pregnancy and diagnosis of pulmonary metastases was greater than 1 year, when multiple pulmonary secondaries were present or when cerebral metastases occurred. The main causes of death were cerebral haemorrhage, respiratory failure and pulmonary embolism.