Purpose: The number of patients having hypersensitivities with dental materials increases continuously. One of the most important allergens is benzoylperoxide (BPO). It is part of the promoting system of acrylic denture-base materials. Aim of this study was to describe the BPO concentration in different denture-base materials after storage and different chemical treatments. Materials and Methods: 3 hot curing materials (Paladon 65®, Heraeus Kulzer; SR-Ivocap®, Ivoclar Vivadent; Kallocryl B®, Speiko-Dr.Speier), 2 self curing materials (PalaXpress®, Heraeus Kulzer; Kallocryl A®, Speiko-Dr.Speier) and one microwave curing material (Microbase®; DENTSPLY DeTrey) were investigated. BPO was measured in the polymer as delivered by the manufacturer, after recommended polymerization, after extended polymerization (1 and 2 hours), after storage in water for 8 days, after storage in artificial saliva for 8 days, and after storage in potassium permanganate, alcohol and ammoniaferric(II)sulphate for 48 hours. HPLC and indirect iodometry was used to detect BPO. Results: BPO was found in all tested denture-base acrylic resins. However, there were significant differences between the acrylic resins (polymer 0.13-1.2 %, cured products 0.05-0.32 %) as well as between the specific treatments and storage procedures (p ® contained the lowest BPO-levels. No reduction of BPO was seen after storage in artificial saliva. The different treatments and storage procedures achieved different results. The strongest effect on the BPO-content occurred after extended polymerization for 2 hours (0-0.08%). Conclusion: Under oral conditions it is unlikely that BPO is released from the investigated acrylic resin denture-base materials. In case of an allergic reaction to the worn denture BPO in the base materials can be reduced by extended polymerization.