We investigated prospectively whether the detection of serum lactate dehydrogenase (LDH) and/or peritoneal fluid LDH levels may serve as a reliable biochemical marker in discriminating ovarian carcinoma from benign ovarian tumors. In this series, postoperatively 20 of 50 patients had a diagnosis of ovarian cancer while the remaining 30 patients had benign ovarian tumor. No significant difference in peritoneal fluid LDH levels was observed between patients with ovarian cancer and benign ovarian tumor (p > 0.05). Serum LDH levels in ovarian cancer patients were significantly higher than those in patients with benign ovarian tumor (p < 0.05). Statistically significant differences were not observed in LDH levels of different histological types of ovarian cancer and different stages of the disease. Serum LDH levels presented diagnostic accuracy with high specificity and may have a potential use as a biochemical marker. Copyright (C) 2000 S. Karger AG, Basel.