The etiology of urinary stones is extremely complex. Because urinary stones arise in abnormal urine, 24-hour urinalysis is often used clinically as an important basis for the diagnosis of urinary stone etiology and monitoring of treatment. In order to reflect the risk of urinary stone formation and to predict the future occurrence of urinary stones, many formulas describing the magnitude of the risk of urinary stone formation have been proposed in the literature. Some scholars have based on the interrelationship between different components of urine and crystal inhibiting components; various different risk formulas, risk equations and risk indices have been proposed to determine whether stones are formed or not. Although it is not possible to predict with certainty the future occurrence of stones by the analysis of different variables of these formulas, it is informative, at least to some extent, for screening or diagnosing patients with stones and for determining in those patients where an aggressive treatment program should be adopted. In 1978, Roberston (23) introduced the concept of risk factors for stone formation based on the theory of saturation inhibition balance of urinary stone formation; six risk factors for calcium-containing stone formation were found in the Leeds, UK area; namely urine volume, pH, calcium, oxalic acid, uric acid and acidic mucopolysaccharides (GAGS). In fact, the main risk factors for calcium-containing stone formation include decreased urine volume, increased urinary pH and excessive excretion of urinary calcium, oxalic acid, uric acid and decreased excretion of GAGS-like crystallization inhibitors. Although each risk factor was significantly different between urinary stone formation or and normal subjects, there was considerable overlap in the frequency distribution of the two groups. Based on the above studies, Robertson proposed a model of calcium-containing stone formation, according to which the prerequisite for urinary stone formation is a period of abnormal urinary crystallization in the urine; during that period, large crystals are formed in the urine; the abnormal crystalluria is due to various biochemical abnormalities; thus raising the risk concept of stone formation. According to its lithogenesis model, the increased pH of urine, increased excretion of calcium and oxalic acid as well as decreased urine volume and decreased excretion of GAGS significantly increase the probability of risk of calcium-containing stone formation. It is now believed that: important factors determining urinary calcium oxalate supersaturation include urinary oxalate (Ox), citrate (Cit) and magnesium (Mg) content; while important factors determining calcium phosphate supersaturation are urinary calcium (Ca), phosphate (P), citrate (Cit) and pH. Citrate in urine inhibits the growth of calcium oxalate and calcium phosphate crystals; magnesium also inhibits the growth of calcium phosphate crystals; in addition, certain macromolecules in urine also play a crystal inhibitory role.