A micro-enzyme-linked immunosorbent assay (ELISA) test and an ELISA inhibition test were developed and used to detect 4 monoclonal antibodies potentially useful for serodiagnosis of cancer. The 4 antibodies used in conjunction detected 73% of 71 sera from cancer patients and 8% of 42 sera from normal persons. Separately, the 4 antibodies reacted to tumors from various sites such as lung, breast, colon, stomach, and ovary. The ELISA inhibition assay may be useful for detecting culture supernatants reactive against tumor-associated serum antigens. Eventually, a panel of monoclonal antibodies detecting various tumors may be obtainable.