This study determined interleukin-10 (IL-10) expression in patients with ovarian carcinoma and in ovarian carcinoma cell lines, and investigated its clinical significance in the development and progression of ovarian carcinoma. Expression of IL-10 in ovarian carcinoma, benign ovarian tumour, normal control tissues and ovarian carcinoma cell lines was detected by immunohistochemistry and Western blot analysis. IL-10 concentrations in sera and ascites from patients with ovarian carcinoma, in sera from patients with benign ovarian tumour and normal controls, and in supernatants of ovarian carcinoma cell line cultures were measured by enzyme-linked immunosorbent assay. The tissue level of IL-10 in ovarian carcinoma was significantly higher than in benign ovarian tumour and normal controls. IL-10 expression was detectable in cell lysate and supernatant from ovarian carcinoma cell lines. In patients with ovarian carcinoma the IL-10 level in ascitic fluid was significantly higher than in sera, and the serum IL-10 level in ovarian carcinoma was significantly higher than in benign ovarian tumour and normal controls. Ascitic IL-10 levels in ovarian carcinoma were significantly correlated with disease stage but not cytological grade. These results suggest that ovarian carcinoma cells are able to synthesize and secrete IL-10, which probably assists in promoting the development and progression of ovarian carcinoma.