The urolithiasis occurs as a result of metabolic and urodynamics disturbances in the metastable medium of the renal excretion of various organic and inorganic compounds. As results of the growth of microcrystalline formation, the process evolves towards uroconcrements, varying as a matter of shape, size, composition and clinical evolution. The analysis of urinary calculi by chemical methods is rather unsatisfactory. Physical, chemical and mineralogical tools are among the methods that are use more and more to establish the composition of urinary calculi. Infrared (IR) spectroscopy investigation of surgically extracted and spontaneously eliminated calculi permitted to find out their qualitative composition. The interpretation of spectra by means of implementing a program on computer, allowed for defining thereby the types of Urolithiasis. Method of IR spectroscopy is a physico-chemical analysis which had as aim to define the types of lithiasis.