Two hundred consecutive patients with malignant pleural effusion were reviewed. The pathologic etiology of malignant pleurisy was: primary lung cancer in 123 cases; five, mesothelioma; and 72 cases secondary to metastatic tumors. Adenocarcinoma of the lung and mammary cancer were the most frequent tumors causing malignant pleural effusion. The modalities employed in local treatment consisted of thoracocentesis in 62 patients, tube thoracotomy in 111 cases with local instillation of adriamycin, MMC, CQ, 5FU, OK432 or talc. Surgical procedures including pleuropneumonectomy or reduction surgery of the tumor with decortication were performed in ten patients. Tube drainage with local instillation of drugs was more effective than thoracocentesis with or without local therapy. Excellent initial results were obtained in patients who received reduction surgery with decortication and pleurodesis. Results of cytologic investigation were positive in 157 cases (78.5 percent). The tumor cells disappeared in 79.4 percent of primary cancer pleurisy cases and 81.1 percent of patients with metastases while disappearance or significant decrease in pleural effusion following treatment was obtained in 75.2 and 77.8 percent respectively. The median survival was 11.3 months in primary cases, and 11.7 months in patients with metastases.