(Di-tert-butylhydroxyphenyl)thio substituted hydroxamic acid derivatives of the formula: ##STR1## wherein X is straight or branched C.sub.1 to C.sub.15 alkylene which may be attached to Y through phenylene, provided that X is not n-butylmethylene; Y is CO--N(OH) or N(OH)--CO; and R is hydrogen or straight or branched C.sub.1 to C.sub.9 alkyl, C.sub.3 to C.sub.9 cycloalkyl, aryl, or aralkyl, provided that R is not hydrogen when Y--R is N(OH)--CO--R; or a pharmaceutically acceptable salt thereof; useful in treating arteriosclerosis, ulcer, inflammation, allergy, or the like.