5-Aryl isoxazole derivatives of general formula (I): ##STR1## wherein: Ar represents phenyl optionally substituted substituted by one or more groups R.sup.2 or pyridyl substituted by one or more groups R.sup.2 ; R represents: hydrogen, --CO.sub.2 R.sup.3, --COR.sup.4, cyano, halogen, alkyl or haloalkyl; R.sup.1 represents: alkyl, haloalkyl or cycloalkyl; R.sup.2 represents: a halogen atom, R.sup.4, nitro, --CO.sub.2 R.sup.3, --OR.sup.4, --S(O).sub.m R.sup.4, --S(O).sub.m R.sup.5, --O--(CH.sub.2)...