A stability-indicating high-performance liquid chromatographic assay method was used to study the stabililty of cefazolin sodium (50mg/mL) in 0.9% sodium chloride injection in polypropylene syringes at 5 deg C and 25 deg C. The concentrations of the drug were directly related to peak heights, and the percent relative standard deviation based on five injections was 0.5. There were three products of decomposition that separated from the intact drug. At 5 deg C, the decomposition was less than 4% when stored for 22 days; and at 25 deg C, the loss in potency was less than 8% when stored for 7 days. When the drug was stored for 22 days at 5 deg C, its pH value increased from 5.1 to 5.3. The pH value of the injection increased from 5.1 to 5.8 when stored at 25 deg C for 7 days. The drug was not adsorbed onto the syringes, and the physical appearance of the injetion remained clear at 5 deg C and at 25 deg C during the study period.