Six patients with malignant effusions, five from adenocarcinomas and one from a melanoma, were treated by intrapleural or intraperitoneal Corynebacterium parvum. In each case there was a definite reduction in the effusions with a significant decrease in the number of malignant cells; in most cases the effusions stopped completely. Although none of the patients lived for more than a year after treatment, they were undoubtedly more comfortable, as they no longer required frequent paracentesis. In some cases the patients lived for longer than originally expected in a state in which the quality of life was acceptable.