The efficacy and safety of intrapleural LC9018 (Yakult Co. Ltd., Tokyo, Japan) with or without doxorubicin (Adriamycin; Adria Laboratories, Columbus, OH) were evaluated in a randomized, controlled trial performed in 95 patients with malignant pleural effusions secondary to lung cancer. Seventy-six patients were eligible for the assessment of efficacy. The response rate for treatment with intrapleural doxorubicin plus LC9018 (38 patients) was 73.7%, which was significantly higher than the response rate of 39.5% for the control group treated with doxorubicin alone (38 patients) (P less than 0.01). The LC9018 group also showed a significantly greater improvement in performance status (PS) and symptoms (chest pain, chest discomfort, and anorexia) than the control group (P less than 0.05). A significant prolongation of survival was noticed in the LC9018 group (P less than 0.05). The main side effects of LC9018 were fever and transient hepatic dysfunction, but there were no serious adverse reactions. These results suggest that the intrapleural instillation of LC9018 can be recommended for the treatment of malignant pleural effusions.