The central hypothesis for this study is that it is safe and feasible to administer intraluminal photodynamic therapy (PDT) to colon cancers, via colonoscopy, in the neoadjuvant setting to induce localized tumor cell death and an inflammatory/immune response with an increased Th1 component, utilizing 5-ALA as a photosensitizer. The objective is to conduct an initial phase I/II clinical study to demonstrate the feasibility and safety of colonoscopic, neoadjuvant intraluminal PDT to colon cancer patients administered 96 hours pre-resection, to characterize the inflammatory/immune response at the PDT treated tumor site, and to evaluate the systemic anti-tumor immune response. The long-term objective of these studies is to provide an easily administered, adjunctive, therapeutic maneuver that lacks systemic toxicity, with the potential to modulate the natural biology of colorectal cancers that have not elicited a favorable anti-tumor immune response and to improve patient survival.