Forty-one patients with malignant pleural effusions secondary to breast cancer were randomly allocated to treatment with either intracavitary talc or intracavitary tetracycline. Of 33 evaluable patients, radiological control was achieved in 11/12 (92%) of the talc group compared with 10/21 (48%) of the tetracycline group (P = 0.022). Intracavitary talc provides effective palliation of metastatic pleural effusions secondary to breast cancer.