The only effective therapy for patients with metastatic soft tissue sarcoma in the lung is surgical resection, with a 5-year survival of approximately 25%. Because systemic chemotherapy has not significantly affected survival in these patients, we began to investigate locoregional chemotherapy. We have previously shown that isolated single lung perfusion with doxorubicin in the rat results in higher lung tissue levels and lower systemic toxicity than does high-dose intravenous therapy. In the present study, we examined the safety of isolated lung perfusion with doxorubicin and its efficacy in the treatment of experimental pulmonary metastases from soft tissue sarcoma. In experiment 1, 15 F344 rats were randomized into three groups (n = 5): group I had isolated left lung perfusion with doxorubicin 320 micrograms/ml in saline solution; group II had left isolated lung perfusion with doxorubicin 480 micrograms/ml and group III with doxorubicin 640 micrograms/ml. All perfusions with doxorubicin were at 0.5 ml/min for 10 minutes followed by perfusion of saline solution for 5 minutes. On day 21, all animals underwent right (contralateral) pneumonectomy and were observed for over 10 days. In experiment 2, two groups of F344 rats were injected intravenously with 10(7) viable methylcholanthrene-induced sarcoma cells on day 0. On day 7, group I (n = 12) had left isolated lung perfusion with saline solution only and group II (n = 15) had isolated lung perfusion with doxorubicin 320 micrograms/ml. On day 21, all animals were killed, and their lungs were stained for metastases. Routine histologic sections from three animals from group II were examined. In experiment 1, 80% of the animals in group I survived contralateral pneumonectomy. There were no survivors in groups II and III. In experiment 2, three animals died after isolated lung perfusion (one from group I and two from group II), and one animal (group I) was excluded because of mediastinal tumor. All animals in both groups had massive tumor replacement of the right (untreated) lung. Group I animals had massive tumor replacement of the left (treated) lung, whereas animals in group II had eradication of metastases in nine of ten cases; no microscopic evidence of tumor was detected in all three animals evaluated for microscopic disease. Isolated lung perfusion with doxorubicin 320 micrograms/ml is safe and effective in eradicating experimental pulmonary sarcoma metastases in this model.