Abstract: Certain new 1-(substituted-hydrocarbyl)-di- and trihalopyrazoles have been synthesized. They possess herbicidal and plant growth regulatory activity. The hydrocarbyl group, i.e., alkylene or alkenylene group at the 1-nitrogen of the pyrazole nucleus has either a carboxyl group, an hydroxymethyl group, an hydroxymethyl lower-alkanoate group, a carboxylic lower-alkyl ester group, a cyano group, or a carboxylic amide group. The new compounds are prepared and isolated by conventional chemical reactions and procedures. An improved reaction for making the new carboxylic acids is described. Weed control methods and compositions for herbicidal use are also described.