Semicritical medical devices such as flexible endoscopes require high-level disinfection between each use, and glutaraldehyde is often used for this purpose because of its favorable materials compatibility. However, workplace safety and the relatively slow microbicidal activity of such formulations remain a concern. Although recently introduced substitutes based on 0.55% ortho-phthaldehyde (OPA), 7% to 14% hydrogen peroxide, and 0.1% to 0.3% peracids are considered less toxic than glutaraldehyde, OPA can be a potential respiratory sensitizer, and the materials compatibility profile of peroxide/peracids at effective concentrations remains an issue. This study describes a high-level disinfectant/sterilant based on 2% accelerated hydrogen peroxide (AHP). It is a blend of stabilized hydrogen peroxide with safe inerts, which act in synergy, and has a 14-day reuse, 5-minute high-level disinfection, and 6-hour sterilization claim at room temperature. Extensive testing of this formulation using nationally and internationally accepted protocols has found it to be a fast-acting and broad-spectrum microbicide in addition to being biodegradable, virtually nontoxic, and free from volatile organic compounds and alkyl phenol ethoxylates. In addition, materials compatibility testing has proven it to be compatible with flexible endoscopes. Therefore, this new chemistry represents a significant advancement in the design of safer and faster acting, high-level disinfectants.