In the present study the modulatory effects of inflammatory cytokines, interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma), on CA-125 release in established ovarian cancer cell lines and in human peritoneal mesothelial cells (HPMC) both grown as monolayers, were investigated. The purity of mesothelial cell cultures were confirmed by the positivity of the cells for vimentin and cytokeratins 8 and 18, and their negativity for markers CD34 and CD68, thus excluding contamination by endothelial cells and macrophages. The preliminary results of CA-125 measurements in the culture medium clearly indicated differences in the pattern of CA-125 expression and release between normal and malignant cells under the influence of inflammatory cytokines. Furthermore, it seems that normal mesothelial cells play a crucial role as a source of CA-125 found in ascitic fluid or in pleural effusions and possibly even in the serum since secretion of this tumor marker into the culture medium was found to be significantly higher in HPMC than in ovarian cancer cells.