A brief overview is given of light distributors developed by our group in Lausanne for photodynamic therapy (PDT) of cancer. We focus on fiber optic devices which have to a large extent been tested over the years in the clinic for PDT of the upper aerodigestive tract, the tracheobronchial tree, the esophagus, the uterus, and the skin. Both surface and interstitial light distributors are discussed. Several different phys. principles for obtaining the desired light intensity distribution in tissue are demonstrated, including the use of specially shaped reflecting surfaces, light scattering and refraction by particles, the use of flexible highly reflecting balloons, controlled fiber core surface roughening, and microlenses. PDT can be improved using \"intelligent\" light distributors, which permit the measurement of the light intensity reflected from the irradiated surface, as well as the dye fluorescence signals. Both are measured in situ and in real time during the treatment. The use of such devices, which can measure photobleaching kinetics, and enable one to adjust the light dose to the obsd. dye fluorescence signals, thus giving better PDT control, is discussed.