Comparison of basic fetoprotein (BFP) with 10 other tumor markers was made with sera from 549 patients with benign diseases and 870 patients with cancers, using BFP-EIA kit and commercial kits for others. BFP-positive rates higher than CEA or CA19-9 were found in various cancers except CEA in cancer of the colon, pancreas and lung, or CA19-9 in cancer of pancreas and bile duct. Furthermore, BFP showed higher positive rates in comparison with AFP in cancer of liver and testis, SLX(sialyl SSEA-1) or SCC in lung cancer and CA125 in uterine cancer. The correlation coefficient of BFP with other tumor markers except for SCC in lung cancer were low (below 0.262) in cancer and benign diseases. The combined assay of BFP with some other makers such as CEA in cancer of the digestive organ, lung, markers ovary and uterus, CA19-9 in cancer of the bile duct and lung, CA125 in ovarian cancer, AFP in cancer of the liver and testis, and PAP in prostatic cancer, showed an elevation of diagnostic efficiency compared with single assay. These results indicate that BFP is superior to other tumor markers for serological diagnosis of various cancer and also available for the combined assays.