The purpose was to investigate the effect of phytohemagglutinin (PHA) on proliferation and cytotoxicity of cytokine-induced killer (CIK). Peripheral blood mononuclear cells (PBMNCs) from healthy donors were divided into two groups. Cells were resuspended and maintained in complete medium containing of 10% autologous plasma. CIK cells were cultured by traditional method in group one. The other group cells were added PHA to stimulate PBMNCs for 24 hours, then cultured like incubating CIK cells. Their cytotoxicity to different target cells was evaluated by (51)Cr release assay. The results showed that the proliferation multiples of CIK and PHA-CIK cells were both high, however, the latter was much higher than CIK with significance (P < 0.05). Cells in each group cells showed high cytotoxicity. At the same high effector/target ratio PHA-CIK cells cytotoxicity was stronger than CIK cells when targets were K562 cells or acute leukemia cells (P < 0.05). In conclusion, PHA-CIK cells exhibit stronger proliferation and cytotoxicity than CIK cells, and the result provides an experimental basis for biotherapy.