Malignant pleural effusions with dyspnoea as their most common presenting symptom are a frequent clinical problem in patients with neoplastic disease. Lung carcinoma is the leading cause, followed by breast carcinoma and malignant lymphoma. The frequency of malignant mesothelioma is increasing in industrialized countries. In this overview, which is based on the ERS/ATS Statement 2001, the diagnostic approach, the differential diagnosis including causes of paramalignant effusions, as well as the therapeutic possibilities are described. Pleurodesis is the most important therapeutic modality, today preferably via thoracoscopic talc poudrage. Alternative local and systemic treatment options are discussed in detail. A special emphasis is put on the epidemiology, diagnosis, treatment, and prognosis of malignant effusions in patients with lung and breast carcinomas, and with lymphomas. Finally, open questions are listed which need future research, which will hopefully improve the treatment and prognosis of malignant pleural effusions.