The spa treatment most widely used in the management of renal calculosis is the drinking of a certain amount of mineral water under certain predetermined conditions of temperature, time and rhythm. These treatments are always indicated unless there are obstacles to the passage of urine or general contraindications. Chances for success are increased if the diagnosis is exact and the stone has been located. The results obtained by various authors are reported and their statistical validity is discussed. Favorable effects consist in: increased diuresis with urine dilution and correspondingly reduced concentration of lithogenic salts and hence supersaturation of urine; reduced concentration of microorganisms; changes in the physiological condition of the renal medulla; changes in inhibitors of crystallization, in urinary pH; mechanical effect on the urinary passages; increased ureter motility; expulsion of small stones and sand; preventive action on recurrences after surgery and after extra-corporeal shock-wave treatment, percutaneous therapy and uretero-nephroscopy.