Formation of uroliths is not a disease but rather a complication of several disorders. Some disorders can be identified and corrected (e.g., infection-induced struvite urolith formation), and some can be identified but not corrected (e.g., hyperuricosuria occurring in Dalmatians that form ammonium urate uroliths), although for others, the underlying etiopathogenesis is not known (e.g.; calcium oxalate urolith formation in Miniature Schnauzers). A common denominator of these disorders is that from time to time, they can create oversaturation of urine with one or more crystal precursors, resulting in formation of crystals. To develop rational and effective approaches to treatment, abnormalities that promote urolith formation must be identified with the goal of eliminating or modifying them. It is therefore important to understand several basic concepts associated with urolithiasis.