L-fucose (L-FC),6-deoxygalactose, is one of rare sugars which naturally exists in the form of L-isomer. L-fucose plays an important role in their physiological and biological functions. It has been well known that L-FC is attached to glycochains of tumor markers such as alpha fetoprotein (AFP) and CA-199. Increment of α-L-fucosidase was detected in patients with primary hepatic carcinoma. Fucolipid accumulation in human adenocarcinoma was abnormally increased and fucosyltransferase was highly active in lung cancer cells. In addition,it has been found that patients with liver cancer and cirrhosis excreted free L-fucose via urine to greater extent than normal individuals. The values of UFC were detected in the urine from 86 health people and 205 people with various tumors. The mean value of urinary L-FC in health people was 177.7 μmol/g.cr(s=56.6, 95% confidence range was 63.8～290.2 μmol/g.cr). The mean values of UFC in urine obtained from patients with hepatocellular carcinoma, cirrhosis, acute and chronic hepatitis, pancreas carcinoma, gastric cancer, lung cancer , intestinal cancer, esophageal cancer were higher than 290.2 μmol/g.cr, having significant difference from normal individuals. The mean values of UFC in urine obtained from patients with mastadenoma, cervical cancer and ovary cancer have significant difference from normal individuals. The value of L-fucose in urine can be regarded as one of the characteristic indexes for hepatocellular carcinoma and canceration of acute and chronic hepatitis. Detection for L-fucose is one of tumor marker tests for patients with tumor in digestive system.