MIP-1a (macrophage inflammatory protein 1-alpha) also known as Chemokine (C-C motief) ligand 3 (CCL3), is a cytokine belonging to the CC chemokine family that is involved in the recruitment and activation of macrophages, monocytes and neutrophils. In this case, chemotaxis?assay used 24-well microchemotaxis system was undertaken to evaluate the chemotactic effect of MIP-1a on the human monocytic cell line THP1. Briefly, THP1 cells were seeded into the upper chambers and various concentrations of MIP-1a was added in lower chamber with a polycarbonate filter (8 um pore size) used to separate the two compartments. After incubation at 37℃ with 5% CO2 for 2h, the filter was removed, then cells in low chamber were observed by inverted microscope at low magnification (×100) and the number of migrated cells were counted using Image J. The migrated THP1 cells in low chamber at low magnification (×100) was shown in Figure 1. The number of migrated THP-1 cells was shown in Figure 2. The optimum chemotaxis of MIP-1a occurs at 1 ug/ml.