SummaryThe authors report six cases of bloody left sided pleural effusion in relation with a subdiaphragmatic lesion. In the first three cases they discover a pancreatic pseudocyst which fistulized into the pleural cavity and produced a very high level of amylase activity. The diagnostic must be proved by the early injection of ultra-fluid contrast medium into the pleural cavity. The three other cases were: one haemorrhagie adenoma of the left adrenal gland, one intrasplenic reticulosarcoma and one intraabdominal reticulosarcoma. In these three cases the pleura was free of metastatic involvement. The authors discuss the diagnostic procedure and the treatment of these left-sided pleural effusion in relation