The authors studied the availability of parenteral solutions of diazepam in glass bottles or polyethylene (PE) containers during infusion through polyvinyl chloride (PVC) administration sets. Diazepam solutions in concentration of 1000 mg/500 ml in 0.9% sodium chloride (NS) and 5% glucose (G5W) injection were infused at a flow rate of 30 ml/h, and samples were taken from the bottle and at the end of the administration set, till 12 hours of infusion. The samples were tested in triplicate using ultraviolet spectrophotometry. The greatest loss of diazepam was observed in all solutions at 30 minutes of infusion (63.5% G5W glass, 60.5% NS glass, 55% G5W PE and 58% NS PE from the original concentration of 200 micrograms/ml). The diazepam concentrations in the containers did not significantly changed. The loss of diazepam from solutions infused through PVC administration sets should be kept in mind in severe clinical situations as status epilepticus, tetanus and eclampsia.