Sacramento VA Medical Center 1 article published in JoVE Medicine An In Vitro Approach to Photodynamic Therapy Evan Austin1,2, Jared Jagdeo1,2,3 1Department of Dermatology, University of California, Davis, 2Dermatology Service, Sacramento VA Medical Center, 3Department of Dermatology, State University of New York, Downstate Medical Center Photodynamic therapy (PDT) is a medical procedure that involves incubation of an exogenously applied photosensitizer (PS) followed by visible light photoactivation to induce apoptosis. We present an in vitro PDT protocol designed to simulate PDT that may be used to study differences in PS incubation and light treatment parameters.