Apoptosis inducers for cancer therapy have been studied. Among hundreds of inducers, peptide anticancer drugs have many advantages such as being not harmful to humans, high selectivity, and dependence on their structures. Naltriben (NTB) is an octapeptide consisting of DPhe-Cys-Tyr-DTrp-Orn-Thr-Pen-Thr-$NH_2$. Several NTB analogues are known. In this experiment, apoptotic activities of NTB analogues with 8 amino acids were tested using flow cytometry. The conformational study of NTB was carried out using NMR spectroscopy and molecular modeling. Here, the relationships between conformations of NTB analogues and their apoptotic effects are reported.