New Boc-protected pentapeptide amides of the general formula Boc-Cys(Boc)-Phe-D-Trp-Lys(Boc)-Thr-NHR, which are analogs of the natural hormone somatostatin, were synthesized. The cytotoxic activity of the new compounds was evaluated against the cancer cell lines MCF-7, PC 3, and HCT-116 by the MTT test, and some of these compounds were found to exhibit activity at micromolar concentrations