The stability of meropenem in various i.v. fluids stored in various containers for i.v. use was studied. Solutions of meropenem were prepared in a variety of i.v. diluents in polyvinyl chloride (PVC) bags, glass vials, and commercial easy-to-prepare infusion systems. Solutions for storage in PVC bags were prepared with meropenem concentrations of 1 and 20 mg/mL; in glass vials, 2.5 and 50 mg/mL; and in commercial easy-to-prepare infusion systems, 2.5 and 20 mg/mL (Baxter Minibag Plus system) and 1, 5, and 20 mg/mL (ADD-Vantage system, Abbott). The solutions were stored for up to 48 hours at 4-5 or 21-26 degrees C. Meropenem concentrations were determined by high-performance liquid chromatography. The stability of meropenem was influenced by the drug concentration; the drug was stable for a longer time in the 1-mg/mL solution than in the 20- and 50-mg/mL solutions. Stability was also influenced by storage temperature; the drug was stable for a longer time in solutions stored at 4-5 degrees C than in solutions stored at 21-26 degrees C. Meropenem was stable for the longest time in sterile water for injection and in 0.9% sodium chloride injection. The stability of meropenem in solutions in PVC bags, glass vials, Baxter Minibag Plus containers, and ADD-Vantage bags was influenced by the i.v. fluid used to reconstitute the drug, the concentration of the final solution, and the storage temperature.