Abstract: Objective: To evaluate the efficacy of thoracic cavity perfusion with Cisplatin and Mannan Peptide in breast cancer pa-tients with pleural effusion. Methods: From January 2002 to July 2006, 55 breast cancer patients with pleural effusion were seen in our hospital.Their clinical data and parameters related to pleural fluid were analyzed.The average age was 52.4 years.Pleural effusion occurred at 38.5 months on average after diagnosis.Ipsilateral effusion was seen in 38 (69.1%) patients, contralateral effusion was seen in 12 (21.8%) patients, and bilateral effusion was seen in 5 (9.1%) patients.Cis-platin and Mannan Peptide were administered through chest tube drainage.Data of survival complications and response to the treatment were reviewed. Results: Twenty-four patients (43.6%) had a complete response (CR), and 22 patients (40.0%) had partial response (PR).Major side effects of the treatment approach included fever, chest pain, nausea and vomiting.The median survival was 10.5 months.Pleural fluid pH (<7.2), Glucose (<60mg/L), and LDH (≥600U/L) showed a association with failure of the treatment.Patients with higher LDH (≥600U/L) had a worse survival. Conclusion: Tho-racic cavity perfusion with Cisplatin and Mannan Peptide is effective in the treatment of malignant pleural effusion in breast cancer patients, with relatively low local or systemic toxicity.LDH is a predictive factor for survival.