Many different analytical techniques, as solid state spectroscopy, thermoanalysis, NMR, etc. have been proposed to solve the problems in the field of urolithiasis. The problems related to these techniques may be overcomed by thermoanalytical methods coupled with the FTIR spectroscopy, that allows to identify and to quantify all the different components of the renal stones. Thermogravimetry coupled with FTIR is a widely technique to characterize renal calculi because of its great sensitivity, reproducibility and accuracy. Moreover, the absence of sample pre-treatments and the short time for the analysis (20-40 min). are very useful for routine purposes. By this method more than 2000 calculi were analyzed.