The present invention relates to a process for preparing 1-substituted 5-chloro-4-methylpyrazoles of the general formula I ##STR1##

with the meaning for R stated in claim 1, in which a 4-methylpyrazole of the formula II ##STR2##

is reacted with chlorine, the resulting mixture of monochlorinated and dichlorinated product is fractionated by distillation, and subsequently the dichlorinated compound is dehalogenated to compound II and returned to the reaction with chlorine.