3-Arylisoxazol-5-ones and 5-arylisoxazol-3-ones were prepared and converted to theN-methyl andO-methyl derivatives by reaction with diazomethane. The halogen in 3-phenyl-5-chloroisoxazole was replaced by several alkoxy and thioalkoxy groups. The 3,5-disubstituted isoxazoles thus obtained reacted withn-butyllithium to form the 4-lithio derivatives, as shown by conversion to 4-carboxylic acids and 4-iodocompounds. 3-Methoxy-5-phenylisothiazole was also lithiated at the 4-position.