Elevation of serum CA 125 levels is associated with malignant serous ovarian carcinomas and has been described in one patient with Meigs syndrome. We present two additional cases of Meigs syndrome with significant elevations in serum CA 125 and report the results of immunohistochemical staining for CA 125. CA 125 expression was localized to the omentum and peritoneal surfaces rather than the fibroma. We suggest that expression of CA 125 and accumulation of ascites in these two patients may have resulted from some common peritoneal process.