Photodynamic therapy, PDT, has mainly been done clinically using laser systems. The use of lasers to treat cutaneous lesions is not necessary. In order to provide a more efficient and cost effective light source for the PDT treatment of cutaneous lesions, a clinical based light emitting diode (LED) system has been developed. The system include a tight density packing of AlGaAs high-brightness LEDs to produce incident irradiance values up to 200 MW/cm2. Initial systems have wavelengths of 665 nm and exhibit a bandwidth of 25 nm, FWHM. Other wavelengths are also possible. The system includes on-line dosimetry through an isotropic probe to permit the use to simply choose a dose, J/cm2. the system has been tested against a KTP/dye laser for the photosensitizer SnET2 to determine its equivalence to a monochromatic source.