IL-10 is an 18-kd polypeptide that has been shown to be secreted by multiple cell types, including T and B cells, monocytes and some human tumors. However, which cell population is responsible for the elevated IL-10 levels in the serum and ascites of ovarian cancer patients, whether ovarian carcinoma cells produce IL-10, and how IL-10 influences the development and progression of ovarian carcinoma are issues that remain unclear. The aim of our study was to examine IL-10 production and secretion by ovarian carcinoma tissues and cells, and to determine its possible role in the cell and tumor micro-environment. The mean IL-10 protein levels expressed in normal ovarian tissue homogenates were significantly higher compared to cancerous ovarian tissue (p = 0.002). Yet, the IL-10 mRNA expression was significantly higher in cancerous ovarian tissues as compared to normal tissues (p = 0.021). The IL-10 receptor mRNA expression levels of the cancerous ovarian tissue homogenates were slightly, but not significantly, higher than the normal tissues. IL-10 immunostaining revealed that in both normal and cancerous ovarian tissues, IL-10 expression could be detected mainly in epithelial cells. In normal ovarian tissues, similar levels of IL-10R were demonstrated in epithelial and stromal cells. However, in cancerous ovarian tissues, epithelial cells expressed higher levels of IL-10R than the stroma. Primary normal and cancerous ovarian cell cultures and SKOV-3 cells secreted similar amounts of IL-10 after 24 hours of incubation. Our results suggest that epithelial cells are the main source of IL-10 in the ovary. Nevertheless, the target cells for IL-10 are different in normal and cancerous ovarian cells. Thus, IL-10 and its receptor could be involved in the pathogenesis of ovarian carcinoma.