The expression levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) were evaluated in normal and cancerous ovarian tissue and primary cell lines (PCL). Seven normal and 10 cancerous, formalin-fixed ovarian samples were examined for TNF-alpha and IL-6 expression by immunohistochemical staining using polyclonal rabbit anti-human TNF-alpha and IL-6 antibodies. Fresh normal and cancerous specimens were also examined for TNF-alpha and IL-6 secretion by bioassay and immunoassay prior to and following in vitro stimulation with lipopolysaccharide (LPS). The levels of IL-6 and TNF-alpha were higher in cancerous tissues than in normal specimens. In vitro stimulation of normal and cancerous ovarian tissues and PCL revealed their capacity to secrete IL-6. Cancerous tissue and PCL secreted higher levels than normal tissue and PCL. Stimulation of both groups with LPS increased their capacity to secrete IL-6. Optimal secretion of IL-6 by the cancerous tissue was observed after 72 hours with or without LPS (10 microg/ml). Normal tissue secreted maximal levels of IL-6 after 96 hours with or without LPS. PCL from normal ovarian tissue secreted IL-6 constitutively and optimal expression was detected after 96 hours. Carcinoma PCL from cancerous ovarian tissue demonstrated optimal secretion of IL-6 after 24 hours. Stimulation of both types of cells with LPS, IL-1 or TNF-alpha increased their capacity to secrete IL-6. TNF-alpha activity was detected in vitro only in supernatants of ovarian cancerous tissue and only after LPS stimulation; optimal levels were detected after 48 hours and 1 microg/ml LPS. Our results indicate that IL-6 and TNF-alpha are expressed in cancerous ovarian tissue at a higher level than in normal ovarian tissues. Carcinoma cells of ovarian tissues are the main cellular source of these cytokines. The conditions controlling the secretion of these cytokines, under in vitro conditions, are different in cancerous and normal ovarian tissues.