This article provides discussion on different light sources and light delivery devices used for photodynamic therapy of a variety of gastrointestinal malignancies. Different laser and nonlaser sources are discussed with emphasis on most commonly used clinical units. The discussion of light delivery devices is divided into several sections, each reviewing the evolution of fiberoptic delivery devices for different gastrointestinal malignancy. A discussion is provided on power meters and wavelength calibration devices used to assure proper light dosimetry. Finally, a short discussion is provided on a technique used to improve endoscopic monitoring of photodynamic therapy procedure during the treatment.