Bactericidal activity of ceftazidime is determined by the time that concentrations in tissue and serum are above the MIC for the pathogens during the dosing interval. Thus, the most effective mode of administration of ceftazidime is continuous infusion. However, this agent is light sensitive which may result in instability when administered by this method without protection from light. Until now we have had no data to demonstrate the stability of this drug during continuous infusion. Therefore, the objective of this study was to provide such data. One gram of ceftazidime was mixed with 1,000 ml normal saline and exposed to two 36 watt fluorescence lights for 24 hours. The distance between ceftazidime solution and light source was 1 meter. Twenty samples (1 g-ceftazidime in normal saline) solution were evaluated. The mean ceftazidime concentrations in normal saline solution were decreased by only 1.69%, 4.44% and 7.19% after 6, 12 and 24 hours after exposure to light, respectively. Therefore, we conclude that the reduction of drug concentration was not considered to be significantly high, and this agent can be administered by continuous infusion.