The adsorption of lorazepam in intravenous admixtures onto 50-mL polyvinyl chloride (PVC) bags has been studied using a spectorphotometric assay method reported in the literature. This method indicated a loss of 7.7% to 9.5% versus a high-performance liquid chromatography (HPLC) assay method developed in our laboratory, which showed a loss of 4.9% to 5.5%. In the spectrophotometric assay method, benzyl alcohol (the preservative in the lorazepam injection) interfered with the assay procedure. The HPLC assay method separated the peak of lorazepam from the benzyl alcohol peak. It also showed that part of the loss as determined by spectrophotometric assay method was due to the absorption of benzyl alcohol. The adsorbed lorazepam was adsorbed in less than six hours and there was no more loss after that. By storing different volumes of the admixture (20, 30, 40, and 50 mL) vertically in 50-mL PVC bags, the loss of drug due to adsorption did not show any siginificant differences.