The results of treatment with intracavitary bleomycin are reported in twenty patients with a malignant pleural effusion and five patients with malignant ascites. The control rate was 17/20 (85%) patients with malignant pleural effusions and 3/5 (60%) patients with malignant ascites. Toxicities were minimal with fever being the most common side effect in four patients (16%. Bleomycin is an effective and nontoxic sclerosing agent.