4-Hydroxy-5-substituted-3(2H)-isothiazolone-1,1-dioxide derivatives of the formula: ##STR1## where X and Y are independently selected from the group consisting of hydrogen, halogen, and C.sub.1-6 alkyl; provided that positions 2 and 6 of the substituted phenyl moiety may not be substituted by C.sub.3-6 alkyl; or a pharmaceutically acceptable salt thereof; useful in treating urinary tract, especially renal calcium oxalate lithiasis.