Thirty-three patients with malignant pleural effusions due to advanced lung cancer were treated by intrapleural administration of LAK cells combined with rIL2. The pleural effusions disappeared in 18 patients and significantly decreased in 12. Three patients did not respond to the treatment. No serious side effect was found in 33 patients. The results indicate that transfer of LAK cells combined with rIL2 in the treatment of patients with malignant pleural effusions due to advanced lung cancer is effective and safe.