A method for preparing a stabilized antimicrobial hypochlorous acid solution by diluting an aged stock solution to provide a hypochlorous acid solution at a concentration of about 50 to about 7000 ppm at a pH range of about 2.8 to about 4.0. The antimicrobial hypochlorous acid solution maintains at least 75 percent of the available chlorine present over a period of about 6 months to about 12 months. The antimicrobial hypochlorous acid solution has medical applications in humans and veterinary practice, both prophylactic and therapeutic. The solution can also be used for non-medical applications in antisepsis and sterilization of surfaces.