Abstract: Objective: To study the feasibility of IL-2 activated HLA haploidentical mobilized al-logenic peripheral blood monocular cells (allo-mPBMCs) in treatment of metastatic or chemoresistant solid tumor patients. Methods: Eleven patients with malignant solid tumor were enrolled, with HLA haploidentical relatives as the donors. After mobilization with G-CSF for 3 days, allo-mPBMCs were collected and activated by high dose of rhIL-2. Phenotypes and lysis activity of allo- mPBMCs were compared using flow cytometer and LDH kit. Multiple cytokines secreted in serum were examined by ELISA kit. Clinical effects were evaluated by CT scan. Results: In the 11 patients, 2.5-4.3×10¹⁰ acti-vated haploidentical allo-mPBMCs were transfused. After mobilization, the proportion of T cells, espe-cially CD4⁺T cells, decreased significantly and the proportion of NK cells increased remarkably which showed a statistical significance. Whereas after activation with high dose of IL-2, except a dramatic ele-vation in the proportion of activated cells which highly expressed CD69 and CD25, no change was found in the proportion of the other cell subgroups. In LDH test, a potent LAK-like non-specific tumorlysis activity was observed against NK non-sensitive tumor cell line Raji. After treatment, the contents of Th1 type cytokines, such as IL-2, IL-12, IFN-2 and TNF-2, rose significantly while the contents ofTh2 type cytokines TGF-β dropped. Eight of the 11 patients showed relief in symptoms, tumor markersin serum or regression confirmed by CT scan after treatment, one of which reached PR 4 months post-treatment. Progression was observed in 3 cases, including 2 deaths. Conclusion: IL-2 activated hap-loidentical allo-mPBMCs possessed considerable antitumor effect, which could give a new light ontreatment of the metastatic or chemo-resistant solid tumor patients.