A hydroxamic acid derivative represented by the following general formula
(1) having selective MMP inhibitory activity, ##STR00001## wherein
R.sup.1 and R.sup.2 each represents hydrogen atom, lower alkyl group,
lower haloalkyl etc., X represents methylene group or NR.sup.3 (R.sup.3
represents hydrogen atom, lower alkyl group, etc.), and R.sup.4
represents C1.about.4 lower alkyl group.