1-[4-(4'-sulfanilyl)phenyl]urea and its various substituted derivatives can be used to decrease the infectiousness of and reduce the mortality associated with organisms of the genus Leishmania which are responsible for a group of conditions known as Leishmaniasis. This heretofore unrecognized use extends to the known derivatives of ureidodiaminodiphenyl sulfones and includes the novel aryl-ring hydroxylated series of sulfanilylphenylureas of the formula: wherein m and n can be the same or different and may each =0 or 1, R1, R2, R3, R4, R5, and R6 are the same or different and are selected from the group consisting of hydrogen, hydroxyl, halo, C1 to C6 straight or branch chain alkyl, halo alkyl, polyhalo alkyl, alkoxy, cyano, amino, alkanoylamino, alkoxycarbonylamino, carboxy, alkoxycarbonyl, carbamoyl, acyl, R7, and R8 are the same or different and are selected from the group consisting of hydrogen, and C1 to C6 straight or branch chain alkyl Z is amino, acylamino, alkoxycarbonylamino, alkylamino, substituted amino or nitro; or its pharmaceutically acceptable salts.