Despite its poor specificity, CA 125 is a widely used tumoral marker. Significant rises in serum CA 125 levels are found mainly in ovarian cancer, but they also occur in other malignant or benign pathologies such as chronic liver diseases. However, in benign pathologies the CA 125 concentrations hitherto reported did not exceed 850 U/ml. The authors report two cases of chronic constrictive pericarditis with ascites and pleural effusions in which a very high increase of serum CA 125 levels (above 1,200 U/ml) was directly related to the presence of pleural effusions.