The somatostatin levels in serum, cancer tissue and its adjacent mucosas were measured in 43 patients with large intestine carcinoma(LIC). The results showed that the somatostatin level in serum of patients with LIC before operation was obviously lower than that in the control group (Plt;0.001)and after radical operation, it was markedly higher than the preoperative levels(Plt;0.01), but still lower than the control value(Plt;0.001). The somatostatin level in cancer tissue was evidently lower than that in its adjacent mucosas(Plt;0.001)and in normal mucosa(Plt;0.001). There was no significant correlation between the somatostatin level in serum or carcinoma tissue and Duke’s stage or pathological types of the carcinoma tissue. The results indicate that the somatostatin has a negative modulating effect on the growth of large intestine carcinomas, thus provides an experimental basis for the treatment of large treatment of large intestine carcinomas with drugs such as somatostatin.