The antitumor effects of the somatostatin structural derivative TT-232 in different rodent and xenograft tumor models are summarized in this report. TT-232 had previously been shown to inhibit the proliferation of a large number of cancer cell lines in vitro and reduce the size of different tumors in animal models in vivo. The effects of TT-232 by different routes of administration and treatment schedules were studied in various types of rodent and human xenograft tumor models. In the rodent tumor models S-180 sarcoma and P-388 lymphoid leukemia tumor the infusion treatment resulted in 76%-100% tumor growth inhibition and in 20%-60% of the mice being long-term and tumor-free survivors. In the aggressive C-26 colon carcinoma and MXT breast carcinoma, the TT-232 treatments resulted in 71%-75% tumor growth inhibition and an approximately 50% increased survival time. The tumor growth inhibitory effect of TT-232 on human tumor xenografts proved to be significant, resulting in 30%-80% decrease in tumor volume and in 20%-40% tumor-free animals. This antitumor efficacy of TT-232 was seen in almost all the tumors investigated. In our study, the route of infusion was shown to increase drug efficacy relative to conventional delivery methods. Our results suggested that TT-232 is an effective and promising antitumor agent.