Photodynamic therapy is a complex treatment for neoplastic diseases that uses the light-harvesting properties of a photosensitizer. The treatment depends on the amount of photosensitizer in the tissue and on the amount of light that is focused on the targeted area. We use a pharmacokinetic model to represent a photosensitizer\u27s movement through the anatomy and design treatments with a linear program. This technique allows us to investigate how a treatment\u27s success varies over time