The most important preventive measure for recurrence of urinary stones is to achieve urine dilution through high fluid intake. Based on the results of epidemiological and clinical studies, the effects of fluid intake and urine volume on the risk of stone formation and prevention of recurrence are summarized. Urine dilution and stone-forming salt crystallization Theoretically, large fluid intake inhibits stone formation by decreasing the concentration of stone-forming components, but it also decreases the concentration of stone-forming inhibitors. In practice, urinary dilution in the body does not significantly alter the secretion of stone-forming factors (calcium, oxalate, phosphorus, uric acid, etc.) and inhibitory factors (magnesium and citrate) or the pH (acidity/alkalinity) of the urine. Chronic dehydration Persistent low urine output is primarily a result of low fluid intake or increased respiratory-skin water loss. Support for chronic dehydration exposures complicate the high incidence of urinary stones. Epidemiologic investigations have shown that high temperatures, intense physical activity, and inadequate fluid replacement are associated with a high incidence of urinary stones, and that the occurrence of renal colic and stones associated with seasonal changes (during or after the hot season) has been attributed to reduced urinary output in the presence of high temperatures.