Monoclonal antibody drug conjugate A7 was prepared from a mouse splenocyte immunized against human colon cancer. A7 reacted with 80 percent of colorectal cancer and pancreatic cancer. A7 was bound covalently to neocarzinostatin (NCS) to form A7-NCS. A7-NCS had strong cytotoxic activity in vivo and in vitro study. A total of 77 patients with colorectal cancer, including the patients with liver, lung and peritoneal metastasis, were treated with A7-NCS. There were some tumor reduction of liver metastasis on CT scan and pain relief. Follow up study of colorectal cancer patients treated with monoclonal antibody drug conjugate A7-NCS was carried out, with comparing to those treated conventional chemotherapy. Survival rate of the patients with postoperative liver metastasis treated with A7-NCS was slightly higher than that of the patients treated with conventional intraarterial infusion chemotherapy. There was no difference between the group treated with A7-NCS and that treated with conventional chemotherapy in the overall postoperative survival. Patients given a higher dose of the conjugate had a higher survival rate. There were no serious adverse effects in the patients given A7-NCS. Human anti-mouse antibody (HAMA) was detected in all A7-NCS treated patients.