Abstract: OBJECTIVE To compare the current relative growth rate method used in vitro cytotoxicity test of the pharmaceutical packaging materials with MTT method, and calculate the relativity of these two methods. To evaluate advantages and disadvantages of these two methods and give a new way of cytotoxicity test in vitro of pharmaceutical packaging materials. METHODS By using extracts of 4 different pharmaceutical packaging materials, L-929 cells were treated for 2 d and 2, 4, 7 d respectively by the MTT assay and proliferation test. The relative proliferation rate of L-929 cells was caculated, and the toxicity was measured and ranked as 5 grades. The data were statistically analyzed. RESULTS Under the condition of this study, 4 pharmaceutical packaging materials showed different grades of the cytotoxicity. Compared with cell proliferation test, the results of MTT assay showed good relativity (r=0.966, p<0.05). CONCLUSION Compared with the cell proliferation test, MTT assay need less amount of the cells and shows as a quick, simple and effective method for evaluating in vitro cytotoxicity of pharmaceutical packaging materials. So it is worth using MTT assay as a standard cytotoxicity test in vitro for the pharmaceutical packaging materials.