An ortho-Phthalaldehyde based convenient, ready-to-use, high-level disinfectant that provides a broad spectrum of kill including Tuberculosis, Hepatitis A (AER), Hepatitis B, HIV-1, and Polio Virus type 1. It can disinfect a wide range of endoscopes and other heat sensitive semi-critical medical devices. When used as directed, it is exceptionally fast and can disinfect in 5 minutes at 25°C in a legally marketed automated endoscope reprocessor (AER) and in 12 minutes at 20°C.