The 23 hepatectomized patients with hepatocellular carcinoma (HCC) were studied. Samples were biopsied from both cancerous portion and from non-cancerous cirrhotic portion at operation. MIB-1 LIs were measured in these biopsied samples. Then the relationships between MIB-1 LIs and pathologic feature, clinical data, and prognosis were investigated. LIs of the cancerous portion (10.2 +/- 6.8%, Mean +/- SE) were significantly (p < 0.001) greater than those of non-cancerous cirrhotic portion (3.8 +/- 2.1%). LIs of the cancerous portion in the patients who were dead with in 18 months after their hepatectomies, were significantly (p < 0.05) greater than those in the patients who survived more than 18 months after operations. LIs of the cancerous portion in the patients whose samples revealed Edmondson & Steiners classification grade III, were significantly (p < 0.05) greater than those in the patients whose samples revealed grade II. LIs of the cancerous portion in the patients whose serum AFP levels showed high level (> or = 100 ng/ml) were significantly (p < 0.005) greater than those in the patients whose serum AFP levels showed low level (< 100 ng/ml). And LIs of the non-cancerous portion in the patients whose thymol turbidity test (TTT) showed high level (> 5K-U), were significantly (p < 0.005) greater than those in the patients whose TTT levels showed within normal range. LIs of the non-cancerous potion in the patients whose zinc sulphate turbidity test (ZTT) showed high level (> 12K-U), were significantly (p < 0.01) greater than those in the patients whose ZTT levels showed within normal range. LIs of the non-cancerous portion in the patients whose PT levels were prolonged (14 sec <), were significantly (p < 0.05) greater than those in the patients whose PT levels were within range. MIB-1 LIs were proved to be a good marker for estimation of biological behaviour of HCC tumors.