Pyrazole derivatives, selective herbicidal compositions containing said derivatives and the use of said derivatives are provided. The pyrazole derivatives having selective herbicidal activity are represented by the formula I: ##STR1## wherein, X denotes a halogen, nitro or methanesulfonyl, Y denotes hydrogen, a lower alkyl or a halogen, Z denotes a halogen or methanesulfonyl, and R denotes hydrogen; an organic acid residue; a lower alkynyl; a lower alkyl or a lower alkenyl which may be substituted by a halogen, hydroxy, cyano or an alkoxycarbonyl; or a benzyl which may be substituted by a halogen, nitro or a lower alkyl.