||An experimental study of hot spots occurrence in railway disc brakes is reported on. The aim of this study was to better classify and to explain the thermal gradients appearance on the surface of the disc. Thermographic measurements with an infrared camera have been carried out on the rubbing surface of brake discs on a full-scale test bench. Based on thermography, a classification of hot spots observed in disc brakes is proposed. A detailed investigation of the most damaging thermal gradients, called macroscopic hot spots (MHS) is given. From these experimental researches, a scenario of hot spots occurrence is suggested step by step. Influence of parameter such as pad stiffness and pad contact length on hot spots developments is studied. Observations give new highlights on the conditions of hot spots appearance. Discussion of the theoretical approaches compared to experimental observations is proposed.