Previous studies have shown that the cancer cell lines secrete multiple cytokines, such as macrophage colony-stimulating factor(M-CSF), granulocyte-macrophage colony stimulating factor(GM-CSF), interleukin-l(IL-1), interleukin-2(IL-2), interleukin-6(IL-6), and tumor necrosis factor-alpha(TNF-alpha). We evaluated the levels of IL-2, IL-6, and TNF-alpha in the ascites of 23 patients with ovarian cancer. These levels were then compared with cytokine concentration found in 10 patients who had benign ascites and also studied the relation between levels of cytokines and clinical parameters. Enzyme-linked immunosorbent assay(ELISA) was used to determine the levels of cytokines in ascitic fluids. The median age of the group was 56, and the median follow-up time was 24 months. The levels of IL-2 was not elevated in ascites of ovarian cancer(30.5 vs 37.2 pg/ml, p=0.083), 1 he levels of TNF-alpha in the ascites with ovarian cancer were higher when compared with ascites of benign disease and was nearly approached statistically significant(91.0+/-20.7 vs 440.2+/-117.9pg/ml, p=0.058). Significantly higher IL-6 levels were detected in patients ascites compared with ascites with benign disease(354.3+/-42.9 vs 5,605+/-1,137pg/ml, p=0.006). IL-6 and TNF-a levels in ascites did not correlate statistically with tumor volume, histologic type or with survival time. IL-6 levels did not correlated statistically with volume of ascites. IL-6 and TNF-a levels did not correlated either. Circulating platelet counts in patients with ovarian cancer were significantly higher than in patients with benign conditions (282.6+/-5 vs 388.4+/-21.2x-10(9)/l, p=0.003). Thrombocytosis(platelet counts>400x10(9)/l) occured in 35%(8/23) of the cases with ovarian cancer. IL-6 levels in ascites correlated signi-ficantly with circulating platelet counts(R=0.427, p=0.042). This study showed that the patients with ovarian cancer have elevated levels of IL-6 in ascites. IL-6 levels were not correlate with disease status in patients with ovarian cancer. However, the correlation was found between IL-6 levels and thrombocytosis. This observation suggest a role for IL-6 in the development of tumor-associated thrombocytosis. A larger study would help in evaluating the potential biological roles and use of cytokines as tumor markers in ovarian cancer.