The change in serum laminin (LN) level and its clinical significance in epithelial ovarian tumor were investigated. The LN levels in serum and ascites samples from 69 patients with epithelial ovarian tumor and 42 cases as control group before and after operation were analyzed by radioimmunoassay. The results showed that the serum LN levels in the patients with malignant tumors (157.85 +/- 14.37 ng/ml) were significantly higher than that in the control group (125.14 +/- 7.03 ng/ml) and in the patients with benign tumors (128.36 +/- 8.75 ng/ml) (both P < 0.01) before operation. The serum LN levels in the malignant group were decreased significantly after operation as compared with those before operation (P < 0.05). The serum LN levels in low-differentiated tumors was higher than those in moderate-differentiated tumors and high-differentiated tumors (P < 0.05). The LN levels in ascites (172.94 +/- 15.26 ng/ml) was significantly higher than in serum (161.34 +/- 6.59 ng/ml) (P < 0.05) in malignant tumors. The serum LN levels in the patients with lymph node metastasis (165.41 +/- 19.91 ng/ml) was obviously higher than those without lymph node metastasis (152.35 +/- 10.34 ng/ml) (P < 0.05). It was concluded that LN levels in serum and acistis were remarkably increased in malignant epithelial ovarian tumors, suggesting that LN might be one of important diameters reflecting tumor biological characteristics.