INTRODUCTION: The aim of this study was to determine and compare the physicochemical stability of two carmustine-containing medicinal products licensed and marketed in Europe as Carmustin Obvius (Medac GmbH) and Carmubris (Tillomed Pharma GmbH). Reconstituted stock solutions and diluted ready-to-administer infusion solutions of the two products were investigated. METHODS: Reconstituted carmustine stock solutions (3.3 mg/mL) and ready-to-administer infusion solutions (0.2 mg/mL, 1.0 mg/mL) prepared in prefilled 5% glucose injection solution PP/PE bags were stored at 22°C or 2-8°C over a maximum period of 66 hours protected from light. Samples were taken immediately after reconstitution or dilution and after 3.5, 6, 8.5 and 11 hours when stored at 22°C or after (12), 24, 48 and 60 hours when stored at 2-8°C, followed by 3- and 6-hour storage at 22°C (60+3 hours, 60+6 hours). Physicochemical stability was determined by reversed-phase high-performance liquid chromatography with UV detection, measurement of pH, osmolarity and inspection for visible particles or colour changes. RESULTS: Carmustin Obvius and Carmubris reconstituted stock solutions were physicochemically stable for at least 48 hours when stored at 2-8°C. Carmustin Obvius and Carmubris infusion solutions 0.2 mg/mL were physicochemically stable for at least 8.5 hours and 60 hours when stored at 22°C and 2-8°C, respectively. After subsequent storage of the 60-hour refrigerated test solutions for 3 hours at 22°C, the carmustine concentrations averaged the 90% limit and fell below the 90% limit after 6 hours. Carmustin Obvius infusion solutions 1.0 mg/mL were physicochemically stable for at least 8.5 hours when stored at 22°C and for 60 hours when stored at 2-8°C. CONCLUSION: According to the physicochemical stability data, the shelf life (95% limit) of the refrigerated stock solutions is 48 hours and the shelf life (90% limit) of ready-to-administer infusion solutions (0.2 mg/mL, 1.0 mg/mL) is 60 hours at 2-8°C or 8.5 hours at 22°C under light protection. These results facilitate the use of both medicinal products in a pharmacy-based centralised cytotoxic preparation unit.